Here are some ideas for uses of accesorys
Vita-kit:Gives you extra health and when reviving a fallen ally you won't lose as much health while your friend gets extra health.
Parrying blade: while shielding you pull out your parrying blade and you shield will break after more hits than normal.
Bomb bandilier: Your time for bomb charge up decreases.
Scarf: It takes less time waiting when frozen.
Monster pockets: You take less damage from the monster that you have in a pocket.
Helm guards: You take less time in stun.
Hope you like there ideas!
No, absolutely not. Accessories are purely cosmetic and should stay purely cosmetic.