ISM yes, or HISM. If it was a grass clump, you only have as many actual meshes as your blueprint. Not too bad.
I think the problem, is that even if you could paint foliage all over them, when you move them, them foliage will not move with them.
Whereas if you use your own system, it will.
Also, if you REALLY care about only having only 1 grass mesh, you could instance it in the level BP or game instance, and pass a reference to that into your BPs.
There hedges are BPs with filleted edges and ISM ivy leaves
I turned on the ‘test hedge’ so you can see the spawn action
