I don't know about you guys, but I can't stand being locked into specific classes.. it's one of my biggest pet peeves of all the RPGs I've played.  Sure, things like talent trees allow for some customization, but they don't allow what I would consider to be "real" flexibility.  The following are my ideas of how an Open Class System could be implemented to allow for considerably higher character customization than other games in the genre.

*As this content is part of an ongoing project of mine on/off over the last 2 years, please keep in mind that the potential balance issues that would ultimately arise from such a flexible system have been taken under consideration for quite some time, but are not the focus here.  When I get to the issue of all things math related, balance will be centered first and foremost around PvP.

Open Class System details:

• Upon character creation: players do NOT select a primary class to be locked into.
• Accessing the Class menu opens to display a single starting point from which all "class" abilities are centered around and branch out from.
• Each character level (Clvl) awards the character with 1 class ability point (among other benefits to be discussed elsewhere).
• Clvl cap < total number of combined abilities among all classes (in order to provide differentiation instead of all characters ending up with all abilities). Example: 7 classes x 20 class abilities in each = 140 total abilities.  Clvl = 50 (Arbitrarily assigned value).  Therefore, in this case, players can pick and choose to fill up to 2 full classes out of those available, +10 extra.
• Class abilities of 20 divided into 5 tiers each.  T1 = 6 abilities, T2 = 5, T3 = 4, T4 = 3, T5 = 2
• T1 houses the first set of class skills closest to center starting point with no prerequisites.  In order to progress to the next higher tier of any class, a certain number of abilities must first be learned (prereqs).
• Upon learning any class ability, player is awarded with a set of attributes (one of multiple ways a character is awarded increased attributes).  The attributes received in this fashion are based on class.

• Sub-classes are also not selected upon character creation, but instead through some other means (perhaps quest related?).
• Sub-classes provide unique benefits that will further customize a character.
• each sub-class provides the character with passive buffs as well as a unique feature.

1. Captain: party leader.  Captains increase their combat effectivness directly correlating with total party size and number of non-captains in party.  Example: a party full of captains will not increase combat effectiveness of any party member.  Alternatively, a party consisting of 1 captain and 4 members of other sub-classes will provide the captain with the largest combat boost.  Unique ability: TBD
2. Fundamentalist: Excels in the use of any and all T1-3 class abilities. Unique: TBD
3. Extremist: Excels in use of any and all T4-5.  Unique: TBD
4. Survivalist: Always receives STAMINA (HP) boost to some extent no matter what the class ability learned.  If the ability awards STAMINA, a % increase is awarded.  If no STAMINA was awarded for a learned skill, a flat amount will be added in addition to the other conferred attributes.  Unique: TBD
5.  Marauder: Excels in the learning and effectiveness of all weapons and their respective "classes" across the board.  Marauders level weapon classes faster than other classes as well as gaining unique access to the highest weapon skills.

I can give you a real world example of a system that has some of these things.

It was in my main MUD called Lostsouls which was an LP mud.

The system wasa hybrid skill and "class" system.  You had a whole host of skills that trained through use based skilling (you could also pay for training to speed things up).  Not all skills were available from the get go.  The sword skill for example was always avaiable and anyone even people with no "class" could get to 100 in sword simply by using it.  But Cryomancy could only be gotten by joining the White Mages.

So the first thing there were no "classes" instead they were called guilds.  Every character started in the "Adenturer's Guild" which basically meant they had no special abilities but got starter equipment.

You had to find the guilds.  They were hidden.  Some were extremely hidden some were well known but just had some trick or you just had to make it out there.  When you found them some immediately let you join some made you go on a quest or find a special item.

Once you joined you basically got a "class" how that worked depened on the implementation of the guild.  Some power were level based as to when you obtained them some were skill based.  But basically all special powers came from a guild.

You were locked into a guild until level 30, which was called Hero level and required a special quest to achieve involving gettting a number of hard to obtain and find item such as catching a vial of acid from the breath of Tiamat, who was both dangerous and hard to find.

Once you were level 30 you could use the guildstrip command.  Which basically put you back into the Adventurer Guild.  There were a few special giulds in which you could never leave.  For example one guild when you joined possessed your body with a demon and made you undead.  You were stuck there.  But you could gstrip from rangers and for be a discordian if you wanted.  You had a real time limit of one guildstrip per week.

Guilds were exclusive you could only be in one at a time.

The other part of the equation was something called associations.  These worked almost the same as guilds, but were not strictly exclusive and usually only gave one or two minor abilities or some utility.  Certain associations could not be done together, a Chaotic associations and an Order based associations could not be had simultaneously.  Also most associations came with some sort of drawback.

For example joining the Explorers was generally easy and usually compatible with other associations.  It gave you the ability to read the stars and not need a compass it also gave you some fire/cold resistance and a bonus to awareness and elude skills.  But limited you to light armor.

The discoridan association gave you the ability to sing from a hymnbook which caused you to regen spell points faster.  It also gave you chaos favor (which has various obscure benefits) and the ability to quote.  Quote was just something where you randomly spouted out some inane thing that other players had entered into the list of funny quotes, such as "Negative, I am a meat popisicle".  If I remeber right this one also wanted you to use light armor

You could join both exploreres and discoridans.  But the discordian would prevent joining the Tyr association as that one was an Orderly association.

EAch association and guild also had its own special chat channel.  Which I found to be a much cooler way of doing things than most MMOs have done.  As the people you regularly chatted with were also people who were part of what you chose to join.  It made that guild feel like a guild rather than a class and the guilds were meant to be an association of like minded individuals.  One guild was the Knight of the Round table.  Which was kind of like a paladin class, but you know the knights stuck together they were more than a class and they left helpful things in their guild hall for other knights etc.  Most people had a soft spot in ther hearts for the guild there had been in.  There was a certain loyalty that got instilled.  Often people guild hopped around to get special skills.  For example many Knights became rangers to train certain skills then went back to being knights.  Because of this there was always a sort of informal alliance there.  Plus they both could use weapon lore in useful ways, Ranger made good spears and Knights sharpened them.

Same thing with associations.  To get into the discordians you had to lay on the altar with Chaos favor and then it would teleport you down to the guild/association hall  people regularly left helpful stuff there for other discordians.  But an Orderly character didn't get the channel to talk to the discoridan other than whispers or whatver and they had trouble getting chaos favor to get down there.

All in all I thought it was a pretty good system with alot of character although I wouldn't claim it was at all balanced.  But it certainly had far more character and kept people far more accupied on real RPG stuff than many class based MMOs.

Your system has already been implemented in a similar fashion in 'The secret world'. Maybe you should check it out?

In principle your system should work. Here are some further points:

- Game must allow for a group of generalists to be as effective as a group of specialists.

- You should also define combination effects for your skills. Firearmor followed by tornado = firestorm.

- Since the player has a huge choice you will have to allow for respecs.

- The skills of each class must truly be different from each other or there is no point in having a choice (other than the visuals).

- The skill / leveling system alone does not make or break the game. The setting, game mechanics (combat, long term progression, crafting...), visuals and quality of implementation is also very important.