I think the first question anyone designing a rulesystem should ask themselves:

Is my rulesystem better, or at least equal, to the good old classic design ?

The classical rulesystem, as seen in D&D, d20, The Black Eye, etc, many MMOs like Lineage 2 etc, looks something like this:

- Player chooses a class at the start of the game, from a fixed array of possibilities

- Player gain experience through solving quests and/or killing opponents

- Player level up when they have collected enough experience, typical towards a certain maximum ("maxlevel")

- A levelup includes various powerups (like more hitpoints, skills, feats, possibly stat improvements)

Also, quite typically, as modern expansions:

- The game has stat(istic)s - values that descibe the general traits of the character (classically Strength, Intelligence etc)

- The game has skills - abilities that can get better (classically Stealth, Diplomacy, etc)

- The game has feats - properties or abilities your character can gain (classically Heavy Armor, Dualwielding, etc)

- Possibly more (such as learning spells on a D&D Sorcerer)

The criteria to decide the quality of a rulesystem are IMHO:

- Diversity: Quantity and quality of different playstyles possible in the rulesystem

- Depth: Quantity and quality of possible strategies, importance to vary strategies

- Balance: Equalness of power between two player characters that had the same amount of progress

- Control: Ability of the player to decide how to build the character

In my experience, the classic design has the best chances to lead to a system of high diversity, depth, and balance.

I really only included the criteria "control" above because there are rulesystems like TES is who manage to leave it out, leading to the feeling you are "monitored" all the time and arent allowed certain strategies because it would level skills you dont want to level. Most other systems offer the player full control over his characters development.

For example, the TES games (pre Skyrim) do perform extremely badly:

- No actual diversity. Stats would ramp up to 100 on everyone. Everyone can choose "main" skills, but everyone can master any skill to the maximum. Thus everyone basically is a Fighter/Rogue/Mage and can reach mastership in all three fields. The only diversity that would stay in the end are the race and birthsign choices. Still this is the second best trait of this rulesystem, because in actual gameplay you can still have a lot of different strategies. There is just no limit in how many you can archieve.

- Below average depth. The magic system is rather simplistic. Several damage types and defenses against damage types. Melee and ranged combat are also rather simple. Crafting didnt have much depth either. The only field that was actually quite interesting was Alchemy, which was so complex you required helper programs to really dive deep into it.

- Nonexistent Balance. This clearly was nothing Bethesda valued at all. A level 1 player can maximize a skill, the only question is if it is not one of the major skills (and in Morrowind, not one of the "minor" skills either). The increase in stats at levelup is very uncontrolled; a character gains between 1-5 points in a stat, which can lead to massive differences in power in higher level characters.

- Nonexistent Control: There was no way for the player to control what he actually wants to level. You swing a sword, you turn into the master swordswinger, even if you actually want to play a pure mage who only sometimes also uses a sword if they are out of mana.

A much simpler system (which is not a classical system) in Vampire: The Masquerade: Bloodlines already performed much better:

- Still below average, but better than TES diversity. Seven classes, of which only two are much alike (Brujah and Toreador shared 2 of 3 ability lines). Actually maximizing everything was kind of impossible, too, so you had to choose and decide. All stats ended at 5, too, but it was hard to maximize that one.

- Below average depth. The possibilities of the system havent been great. It IS a rather simple system, after all.

- Balance quite weak, but definitely there. The paths have not been perfectly balanced at all, but after a certain amount of gained xp you had gained power and at least the idea of balance was there.

- Full control. You absolutely could decide what you wanted to progress.

TES is a single player game, and I feel it's essentially intended to be played up to around the halfway/quarter point of maxium advancement.   Since after this point due to quest design you're going to have to follow stories you're original character never would have(mage guild, televanni, fighters guild, neverrar, ex-vampire, ex-werewolf, thiefs guild master, dungeon delve-er millionare, and still a super-cute-perky-bubbly adventurer).   All those titles are insane.

_____

I think you could have some interesting advancement if you were to just completely remove levels.   Then relay solely on perks and character statistics for power.   Sure you'd need to find a way to change how you increase statistics but you could easily tie it to crafting, for instance food(a reason to go to the tarvern).   And you'd need to find a way to get new perks but that could easily be tied to gear, titles, and/or uses perk-points created from increasing statistics.