Doesn't look the greatest but its getting better! A mech like unit would be cool. A kind of Piranhna plant like body with green/brown tentacles/roots to allow it to move. Shoots globules of green enzymes and acids that essentially dissolve said target. As for the brain, instead of a little jar filled with green goop possibly make into either a tree like structure (attaches to ground) or, a pulsing core with thick corded vines coming out of it. (attaches to ceiling)

As for gun suggestions I would place most of my bets on Acid/paralyzing/spines for bullets/projectiles. Melee weapons could include pincers, stingers, and blades.

Will sketch up some ideas when i get some free time.

Ahh, leave my BIO faction to rot until i have the patience to make neough frames to make things alive.
Or, learn enough scripting to make a decent thing.