I really love your designs 
As for the issues with the support removal, do you use an AMS? In that case, you could use a concentric PETG support interface with 0mm z-distance for PLA and vice versa. That should work a treat on a dome geometry.
I have not had much luck with PVA, but that was before Bambu offered any. I used very well dried (!!!) Fiberlogy BVOH to great effect with PLA though. But again, that was before I discovered the PETG-PLA support trick in the forum.