[Suggestion] One item Engineers really need.

It's an area denial tool and helps protect bases. In PS1 you could put down several invisible turrets which would automatically activate and kill people rather quickly. These would be used to defend the outside of bases, particularly the area around the back door.
Moving through unfamiliar terrain was a risk, you generally had to be really careful when entering an enemy sphere of influence. Right now with bases being so poorly defensible to infantry pouring in, it might help.

Please no. From other games i can deduce that stationary aimbots will generate whining equal to division of power by frequency of encounter. Maybe if they had like a very narrow targeting angle and reduced range, otherwise:

short anwser: no.

long anwser: nooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo.

Nerve gas canisters triggered by tripwires.

According to the science of the game you dont have to replace the MANA, just press B