nevercast
commented
6 years ago I think symmetry copies are handled slightly different internally, and doing as you suggest would mean that the 3R would just be 3*1R internally. Making this behave as expected when you pick the item back up could be the difficult part. But I can't be sure of that, I just think I've heard about this issue before.
What I mean by that is: let's say you have a part placed with 6R symmetry, and want to place something on that with 3R symmetry — like 6R, but only every other one is placed. That is to say, allow child parts to have symmetries that the parent parts' symmetries are divisible by (i.e., 10 would allow 2 and 5, 12 would allow 2, 3, 4, and 6, etc.). Currently, and in stock, it only allows exact matching symmetry or no symmetry at all. Not sure if this is an unavoidable result of the game's internals, though…
Along these same lines: allow MM children on R parts where it will work. This might be a bit complex to figure out!