I will put this on the RFC list, but it will be completely at the bottom for now.
Yes, of course.
What would be the use case of supporting Xisf for you since you request this?
The case would be working with both applications (in both directions). For starters, anyone with XISF libraries would be able to use his/her subs without prior converting. Furthermore, I think it’s very plausible that power users will use both APP and PI. My RfC will lower the threshold for doing so.