Returning to an old game idea, I've been considering the controls for first-person close combat, which is always rather tricky (as there are elements it can't capture that 3rd person can). Although there maybe a 3rd person view as well.

I suppose I'm aiming for a "simple" yet "diverse" system ... yeah I know, those two don't necessarily mesh, but here are my thoughts.

WASD movement, mouse-look as per standard FPS.

M1 clicked performs a light attack.

M1 clicked repeatedly leads into a combo, initially a combo will be two to three moves but as you improve skill (RPG-wise) you unlock further moves to the combo chain.

M1 held down draws weapon back ready for a heavy attack.

M2 held down blocks with either a weapon or a shield.

M2 clicked at the right time will perform a parry that may have benefits liking leaving the opponent open to a powerful attack.

Some other maneuvers either possessed or learned throughout the game.

Running forward + Attacking equals a special dashing/charging attack.

Crouching + Attacking performs a sort of leg sweeping attack.

Jumping + Attacking will cause a variant of a normal attack, usually to strike from above (oddly enough)

Run + Jump + Attack for a leaping extra powerful attack.

Crouch + Attack after jumping or falling for a plunging attack.

And possibly run ... than crouch + attack for a low sliding attack? Crouch than jump + attack equals a rising attack? In a way its kind of fighter game-like, or rather I looked at old-style beat-em ups like Golden Axe and Streets of Rage that allowed you to perform a number of moves on a few buttons and where usually much simpler than complex Street Fighter specials.

There will also possibly be elements like dodging (always wondered how to do 'rolling/tumbling' in first person) possibly with a double tap of the appropriate WASD key.

There are also special attacks binded to a hotkey that can be learned ... from simple stuff like 'Kick' to 'Whirling Blade' (whirling around in first person?).

Does this seem like a reasonable approach? Any problems? suggestions?

The way I see it is you're making a traditional beat-em-up game with first person view and mouse controls. Looking at it from that angle the question arises what is the difference?

In your system the player has besides executing attack and defense strategies also the added task of keeping the opponent visible and aiming for him while in traditional beat-em-ups keep the players usually visible all the time. You are shifting focus from executing moves with millisecond precision to fps-like cat and mouse game where you are trying to constantly move out of harms way while keeping your aim on the enemy. Could be entertaining gameplay for hardcore fps fans but I see this as something with very steep learning curve. Duels would be frantic competitions on circle strafing around each other changing direction, jumping and crouching randomly so the opponent misses with his aim. This seems to be trend in FPS games but there's no really accurately predicting how the final gameplay will be until you made the game and put the different aspects like dodging, blocking and counter-attacking in balance.

Another thing I find a bit inferior to the traditional beat-em-up camera is the fact that you don't get a good sense of the character positions, actions they are taking and attack ranges from first person view. Was that punch even close to coming in contact? Why didn't I hit with that low kick, did he jump?

But first person view in general does tend to make immersion stronger so you might still be onto something there.

Yes I can't really argue that there is a reason first-person would be superior, very much why I decided that if it came to pass I'd also attempt to a third-person mode. Its very much just designer preference, I want to be able to look out at the world through the game characters eyes.

Just a thought, would a target-lock system like Zeno Clash be a good idea?

Can I suggest creating an item specific actions (equipped weapons means attack controls, equipped shield means block controls). M1 and M2 could correspond with left and right hands of the character.

Brink used a very intuitive system for evasive maneuvering. If you added attack controls to a system like that, I imagine it could be a lot of fun.

You might try a toggled movement system as well (Double tap W key to toggle moving forward). The reason for this is the ability to look in a separate direction from the direction you are moving (really useful for using melee weapons) and could make a targeting system really interesting.

Here is the dev about Brink's S.M.A.R.T (smooth movement across random terrain). Not a perfect game but a pretty impressive system in my opinion.

Have you played Chivalry? It has so far (in my opinion) the best first person melee combat.

M1: horizontal swing. (Hold for charge up for a stronger attack)

M2: Block

MWheel Up: Over Head swing

MWheel Down: Forward Stab

You have to time blocks with your opponents swing (You can't just hold your sword in block position)

You can duck under attacks

You can feint an attack by canceling your swing with the block button. Which causes your opponent to waste their block if they're tricked.

You have to be spatially aware of how your swings are going happening since your attacks do a lot of damage to team mates.

Attacks are slow and missing the appropriate timing can get you easily killed.

It really exhibits cautious game play where you have to decide where and when to engage unlike say TF2 melee where you just run in swinging.