Hey, this is a cool idea. As far as the pysics go, cells "attack" in several ways.

Some use phaygocytosis (engulfing another cell)

some use a method where they penetrate the cell wall and insert a capsule that bursts and releases harmful chemicals

others bind to specific sites on the cell and transform it

and many others . .

I am not sure how much the A6 physics engine would help with this, but I haven't used it very much. It seems like you would need to do a lot of scripting, but it is still a fun concept.