Blacksmith/reforge npc.

Since the game demands dedicated characters for walls / towers / dps etc I would suggest a reforge/blacksmith npc.

As you reach nightmare you need to play the levels using a dps character and all the loot that drops got magical attributes that is connected to that class. So if I use a monk dps I can't improve my wall squires gear due to the lack of magical stats.

So my suggestion would be to add a npc that can reforge the gear ONCE to another class. It keeps the main resistans/hero health / damage etc but the magical attributes get randomly changed. Maybe costs 5.000 gold or 10.000 gold. It would remove the need of having multiple dps characters just to be able to improve all characters.