I mean, we could do a combo. Some basic starter classes, branching into more freely picked secondary specializations that I'll write up a couple of (When we approach the more appropriate time anyways, I won't bother doing it right away) the branching classes and then whatever holes there are, players can fill in.
As of now, I know at least four things I'd like in the bunch.
Warrior - More spongy, armor based, able to use shields efficiently and learn shield skills, very versatile
Rouge - Low HP, great burst damage potential, but low DPS, so not good for crowd control. Would be able to use one or multiple light blades, thrown weapons, and bows/crossbows.
Sorcerer - Offensive magic class. Would start out with two spells of the player's picking, would likely fall into elemental categories.
Cleric - Healing class. Low HP, would start out with a single healing spell and are able to use a one-handed weapon, though in most cases, it'd be for self defense.
At a branching point, I'd assume it'd look something like this.
Berserker - Significantly increased strength and health, based around heavy weapons, would be something of a crowd-control class, would have some self-buffing skills
Fencer - Single-weapon dexterity-based class. High single-target capability, primarily based around precision and hard-hitting armor-penetration-based attacks. No buff-skills
Knight - basic tank class. Crowd control and hit-absorption, agro-skills and whatnot.
Assassin - Increased single-target potential and more efficient sneaking skills. Skills would revolve around hitting weak spots for massive damage, but the class would still be very weak to opponent attacks, and would lose its ability to use bows/crossbows, but would still be able to use throwing weapons. Self-buffing in the form of stealth-skills, and would have crippling debuffs
Sniper - Pure archery-based class, would get a significant damage-up for ranged combat, but would lose most of its stealth-skills, with some exceptions. Would likely have a small self-defense weapon, but nothing grand.
Hunter - Something of a mix of the prior ones, maintaining good stealth capabilities, and staying able to use just about any weapon in the game. Would be more consistent DPS-based than the two prior.
Thief - Less powerful than the assassin, but would have passive loot-based abilities that would increase things like gold find, making it a valuable asset despite being more or less a continuation of the rouge class.
Elementalist - Increased elemental damage, debuff chance with elemental spells in the form of causing per example burning effects, and decreased mana-cost for elemental spells.
White mage - Healing and team-buffs, significantly increased mana pool, would have some offensive spells as well, though not as many as other alternative mage classes.
Black mage - Would branch away from Elemental spells for other alternatives, most of which easily cause debuffs, but have decreased accuracy, a good asset for tougher battles, but fall shorter than the other alternatives for extended, multi-enemy fights.
Red mage - Most versatile, the jack of all trades of the mage classes. Can learn just about anything, but suffers from a smaller mana-pool and somewhat decreased potential with all types of spells, but can on the plus side be used for just about anything, provided mana-management is done well.
White mage - See above
Some buff-based class - Don't have a name for it, but would be the main buffer of the group. Specializes in party-buffs, and has a good mana-pool to take from and fair cooldowns, but the spells take time and leaves the mage vulnerable.
Saboteur - Heavy group debuff class, would be based around debuffing enemy parties. Not so good for boss battles, but can make hunting for loot in tough areas a breeze if combined with the correct other classes.
Do note those were just some examples, and not necessarily an accurate representation of a finished product, plus, there would be the room to add more under-classes. Some would likely be approachable from several initial classes, such as the white mage.
A bit about how gameplay would work (As I have it in my head right now anyways)
About HP: HP is explained through blood. There is no clean-cut health gauge. When you take a hit, you bleed. Blood loss will cause you a number of issues, but won't instantly kill you unless the hit is at a vital spot. Bleeding can be stopped with cure-spells that healing-classes possess, but it won't compensate for blood loss, so even if your cuts have been patched up, you'll still experience the fatigue from blood loss if you've lost a lot of it, but you won't die from it.
About mana and magic: Mana is required to use all spells, as well as that, spells have varying cool down times. Most offensive-based classes will have short cooldowns, while classes primarily focused around other skills such as healing will have longer offensive-magic cooldowns. When a mage is out of mana, he/she will not be able to practice magic. Mana regeneration can be increased through some means, but it is not viable to start messing around with it mid-battle. If a spell is attempted while it is still on cooldown, the mana will be taken, but nothing will happen, making it an absolute necessity to learn how long you have to wait before re-casting spells.
About eating and carrying capacity: All players are required to eat, drink, and rest like they would in the real world. A player will die if they go three days without water, and will notice significant debuffs if the character goes thirsty for an extended period of time. He/she can also go three weeks without food, but will experience extreme fatigue and other debuffs as the hunger prolongs. As far as weight handing goes, all characters are issued one bottomless bag in the beginning of the game. Contrary to the name, the bag is not actually bottomless, but can hold a significant amount of smaller items such as food, water, and healing items, just to name a few. For bigger items, characters should get a bottomless backpack, which can hold a lot of larger items with little trouble, and the weight of the items is decreased by five, making more heavy carries a lot easier. A character can alternatively rent a beast of burden for the day. The BoB will carry items for the player and stay out of fights, and will automatically pick up valuables and add them to its stash. If its satchels are filled, it'll teleport back to the player bank and deposit the items before returning about five minutes later, a valuable asset for longer trips, but they typically take a percentage price, so being decisive about what you give the BoB is key, since giving it a very valuable item to bring home could cost a lot more than throwing it in your bag.
Any questions or requested additions?