If you can make the engine very close to the pivot point it could help reduce the effect of not having the engine on the suspended part (the engine to close to the wheel would be a pretty large unsprung weight). What I mean basically is, the engine being the most heavy part of the car, having it mounted where it is not really suspended by the suspension would not be ideal I think
I didntthink about in details so I dont know how it would work, but ifyou make the swingarm extend a little further of the suspension axis, and hold the engine just over it (the suspension axis) maybe it would have almost the same effect as having the engine mounted on the chassis?
Here is a quick mspaint drawing
I dont have autocad on this computer lol
Orange is your engine
blue the chassis and red the swingarm.
Brown is your engine support, bolted to the swingarm. Green is the swing arm pivot point. You could play with the engine position (forward-backward) and see what gives the best behaviour when driving it.
Frederik