I don't know if more is better, in this case, and not just complicated...
I like having overall tiers of guns. In the first, the MP5 was overall very weak, but was very effective in close-up duel situations. I loved carrying it around as the one gun that can save me. And it was great, because everyone always choose the two best overall guns, leaving me with that particular advantage. However, if you add more meaningful dynamics, it could easily alter the strength of guns. I don't know why its even worth bothering. More options=/= better.
I think this can be achieved in this game, though I don't know how the melee actually damages enemies in conduit 1 & 2.
Every melee would be an invisible beam of damage that has values of reach power speed delay and stun (a screen shake); each gun would have its own values:
Smaller guns have faster melees with little delay to do another melee but weaker damage no stun and shorter range. Medium sized guns have moderated values for all aspects. Large weapons (smaw, phase rifle, carbonizer) have better reach power and stun, but slower attack and a slight delay to do another melee.
Its all numerical values, there is no animation difference, and the values are not necessary too different from a pistol to the smaw, just slight changes.
Unique melee animations or even especial moves are for the next game.