The skill section is really where I think your attributes show their limitations. Having abbreviations "P" "M" and "MP" is a drawback in and of itself, but sometimes it isn't clear why any of them is chosen; for instance Larceny being P rather than M, or Profession - Artist being M rather MP, both seem off.
A common thing you'll find in the game: gray areas. This is why Rule Zero is explicitly stated, and players are encouraged to create character concepts for roleplaying, before worrying about rolls. Regarding skills, while I'm tempted to put more emphasis on using a
relevant ability instead of assigning them, doing so would make the game even more gray.
Larceny: I chose Physical because the skill includes several important physical-related talents: being silent, picking pockets, and sleight-of-hand. It also includes several talents that might be more Mental: hiding, lockpicking, and forgery. The difficulty, of course, is that Physical, Mental, and Metaphysical are all hopelessly intertwined, at least as far as characters are concerned.
Profession-artist: does the soul inspire art? Sure. Which would make it an MP skill. But artists also rely on training, observation, and concentration, which point toward the Mental ability. Anyone playing the game would be welcome to mod the skill, to make its relevant ability Metaphysical, which leads us to...
More, although my first thought is, "Well MODOS is modular, I should just be able to change it," it's really tough to expand the attributes on a skill-based system which ties attributes directly to skills. This triumphirate philosophy is seeded throughout the text, and if you don't like it, you're better off selecting a different game, because there is so much that needs to be altered and rewritten.
Changing relevant abilities on skills is easy. Expanding the abilities list is more complex. The simplest way to do it would be to introduce one new ability, and create new skills for it, while reassigning others, until each of your four abilities has a fairly even mix. Dividing Physical into Strength and Dexterity is more complex, because you'll slant the entire skills system toward physical applications (having two physical abilities with only one mental and one metaphysical).
Note, though, that I've divorced the abilities from the other wings of the game (namely combat and magic). For example, initiative is determined by whatever your best ability is, not Dexterity. There's no damage bonus that is tied only to Strength. You don't get more skills based on your Intelligence. You don't get bonus spells based on your Intelligence, Wisdom, Charisma, Mental, or Metaphysical.
However, each ability has its own flavor. Physical is intimately involved in combat, and is the most easily damaged ability. Mental is harder to damage, and can be used (via a skill) to repair Metaphysical, as well as extend spell durations. Metaphysical is the hardest ability to touch, but you'll be damaging it a lot if you cast spells - since MP health is used to power spells.
In the equipment section, you may want to reconsider having gold be the basic unit of coin. It was never thus in any society I have ever known; silver is a more plausible generic coinage.
Good point. Under consideration.
Your usage of variable damage isn't plausible in any sense, although I can see that gamers may be so accustomed to saying "but my two handed sword is really big so it hurts more than when I cut your throat with my dagger."
Granted, a dagger can kill just as well as a claymore, but note how damage is defined in the game; damage is more accurately described as a measurement of distance from death, than it is a measure of how many cuts and scrapes a character has. (Another roleplaying opportunity...) By the way, a dagger can benefit from the Backstab perk, while a zweihaender cannot. Additionally, if the scenario is that of a stiletto-related assassination, the GM could declare that death (well, mostly death) is determined by a one-roll contest, instead of extended conflict rules (combat), and apply bonuses based on degrees of success.
I think you should check out Dragon Warriors' spell list. Even before I knew what they did, Shadowbolt and Deathlight were spells I wanted to cast. In fact I want to cast them right now.
Cool spell names are outside the scope of this part of the project. I need a stable, flexible foundation. Great example, though. And thanks for the responses. Let me know if my replies change your perspective at all, and I'll get to your further replies soon!