I was thinking... like ya do.... and this was my thought.
Replace the Shield only slot to be a usable item slot instead which would allow the following.
Dual Guns... Rate of fire is a gunners bread and butter... BUT I'd suggest they have to be two identical guns. Hence, if you don't have a silver six in your normal weapon slot... you can't have one in your shield spot either.
Bombers... Restrict it to Gremlin Grenades only.... and you can't use them unless theres a bomb in your normal weapon slot.
Swords.... Two Swords at once??? NAH... Swords don't benifit from thisi mod unfortunately... stuck with shields.
BUT.... I do have another idea.
By doing this you can have TWO HANDED WEAPONS!!!
Sword users.... Wouldn't you like to have a giant battle axe? Grim Reaper Sythe or Naganata??
Gunners.... SHOTGUN.... nuff said.
Bombers... ..... idk ...... Grenade Launcher or Gremlin Flame Thrower?
TWO HANDED WEAPONS =/= Lockdown
Double the guns, double the damage. Enemies won't have a chance, OP.