Fighters and other melee/ranged combat classes are always about how you build them and how you deploy them. A lot of the stuff in this thread is neat and cool, but you also don't want to bog down the game with an insane number of rules and minutiae.
This isn't D&D anymore in other words.
Attacks of opportunity, the ability to use defensive actions like counters, parries, etc all good. The discussion about chain or combo moves is a nice idea. Maybe something like a Hamstring attack that does lower damage but makes the enemy "vulnerable" to a power attack that auto crits or some sort of status effect move like a stun or disarm. Or maybe even a charge attack that if it hits gives you the option to do a tackle move. Or ala many games like World of Warcraft when you parry or block you can counter with X attack.
But things like long swords get penalties versus chain, rapiers do less damage to plate, etc. Shields give bonus ac when worn on the back. No. The simple fact that only bludgeoning weapons work on everything make them the defacto best weapons in the game for no other reason. Realism is nice, but it is a fantasy RPG.
I would also suggest staying away from crit specials unless they were maybe tied into skills a player can learn. Instant death should be a no no either way, it is just too overpowered unless you make it so uncommon it just about never happens. Maybe as a very high level skill that requires under 50% enemy HP if it has to be there at all.
If you want weapons to have a different feel stick to the basics. Weapon reach, speed, damage, and crit multipliers. If you really want to make weapons more unique than that give them bonuses to certain skills, such as Maces give a bonus to a skill that causes stuns, slashing weapons give a bonus to moves that hamstring or bleed an enemy, two handed or "spear" weapons give bonus damage on charge attacks, etc etc. If you have to have reach weapons then you must give them real penalties when used inside their reach zone. I don't mean like a minor minus to hit, I mean like a reasonable hit penalty and a damage penalty. That way you are forced to use them tactically instead of just as regular weapons with a better range.
Options are great, but keep it simple and based around character development, not gear loadout. Not everyone knows D&D and with the license not being involved in this game I wouldn't expect them to follow the old Infinity Engine games rulesets. Lastly if you are going to talk theoretical damage numbers don't say 10+2d10 just say 12-30. Yes there is some mathematical difference in the average between the two but, again, no D&D license and making the game clear and more accessible is pretty important. While Project Eternity is definitely a nostalgia product it needs to be able to bring in gamers that have never rolled a d12 or played Baldur's Gate too.