Cross staff limitations ?

oh Daniel, this is then going to be my n°1 request on the wishlist.
I really need to be able to cross staff between any kind of staves.
not even pitched instrument and a 5 line presentation ??

Also, I found that I needed to be able to use different presentation types within the same player.
like a 5 line for an instrument with another instrument staff in grid, etc.

I have to put this revision work on hold then.

Is it possible at all for a future upgrade ?
best

Yan