I've been bitten before, by thinking that I could lump things together, and then later finding a need to separate them. I don't see a reason either, at least not at this moment, to separate the Transform options, but, you know......I'm thinking whether i need to separate the options for copying Transform stuff, like position, crop, etc. Personally I don't think I need to separate them. Just have a "Transform" option and that will copy the bounding box size and crop, similar to what the "Copy/Paste Transform" on the context menu does.
Maybe you could have an overall checkbox that disables the individual ones? Even if overall defaults to off, the individuals should probably all default to on.
Similar here. I don't see a need at this moment, but......I guess this method would also allow automatically hiding the new sources as the sceneitem visibility is also sceneitem-based, though i'm not sure if that's going to be useful. There also might be a short time interval before it gets hidden.
A short time interval is probably okay, depending on how long it really is. Longer if you put a note to that effect next to the checkbox.