Are there stats?
There are always stats. But can you see them or change them?
We need to decide on that soon. On one hand, it'd help create variety among the characters, along with second jobs. On the other hand, in most games there tends to be one optimal build for each class. I don't want that to happen. (and if I did want that to happen, I'd just automatically have each character have the best build for his class).
All stats need to be useful to all characters. Mind you, a fighter would need strength a lot more than a cleric would, but they'd still be able to carry more stuff. If you really wanted to play a mage with a strength of 5 (or whatever the minimum is) you could. But if a slime bunny draggon dropped a 50-pound ruby, you certainly wouldn't be able to carry it back to town to sell.
Conversely, a magic user would need a high mental score, but how would a fighter use it? Perhaps secret passages are more obvious if you have a high perception? I mean, you could follow another character through the passages, but that'd be realistic too. It'd help you identify magic items, as well.
Would there be social stats (eg. Charisma)? Only if there were a way to make them useful. They don't really figure in to the "walk into a field and kill what's there" mechanic. Since the game is group-oriented, higher social skills may give you a slightly higher share of party xp, better quest rewards, new quests, different solutions to quests, and, if you're of the Leader class, bonuses to your party's attack and defense.
Social skills have no effect on players, of course. If you're rescuing a peasant from marauding slime bunnies, it wouldn't make a difference what your stats were, but it'd probably be worthwhile for a party to have a character with high Social stats to do the talking when you're dealing with the local baron. And the prince won't even talk to you unless your social score is above 30. An all-social party won't be balanced with an all-physical party, but a mixed party (say 3 physical, 2 mental, 1 social) would do much better than either.
I figure a social character would get access to high-reward quests long before a non-social (anti-social?) character would and should be able to gain levels at about the same speed. That fetch quest that gives 30,000 xp? A gladiator would get it at level 35. A dancer would get it at level 15, when 30,000 xp means a lot more. (Or they might both get it when their social score reaches 15, which would be approximately the same for most characters). Availability for quests would be based on social, level, or social + level.
So yes. Let's say there are mental, physical, and social stats. Or those three items may be the stats. Should physical be broken up into, say, strength, agility, and toughness? Perhaps. But I'm not sure how that'd balance against mental and social being just one stat.
I don't think accuracy should be a stat; in normal play it wouldn't matter much, and I see no point in allowing players to make characters that cannot hit anything or players that can hit enemies before they can do any real amount of damage to them.
Could you spend stat points on class skills? Interesting. If you got, say, 2 points per level definitely. If you get 1 point every 4 levels, then no - it'd be too fine a line between 'worthwhile' and 'unbalancing' once you put ten points into it. There may be certain special skills that you can (only?) get by spending stat points, but you couldn't do that every time you get points.
You would be able to increase your stats as you went along, and you'd also be able to reassign one point per level if you needed to. The stat system should be moderately forgiving. As you've seen above, you can min/max things, but you become more dependant on your party to help you. The mage in the first example would do a lot better if he had a high-strength character in his party.
What is the stat range? Minimum of 5. Let's say you start out with 8 extra points to distribute as you see fit, and get an extra point every other level (and the ability to move one point around). And you cannot trade them in for skills or abilities.