This whole discussion is quite pointless to discuss abstractly.
You should rather make a 3rd person prototype
and try out the different modes of aiming, shooting and moving.
and try to balance them until they are fun.

This is a typical test + tuning issue.

Some small recent games of mine:
Griefer 4k http://damocles11.byethost9.com/griefer4k.html
Kobold 4k http://damocles11.byethost9.com/kobold.html
Cave 4k http://damocles11.byethost9.com/cave4k.html