Not necessarily for v4 but two features I think would be golden!

1. Some kind of notification of a conversion of a solid to joined surface. Even turning the Joined surf text at the top right to red would be useful. Sometimes I destroy a solid and I do not even realize until much later when undoing is a pain. It's especially painful after a fillet, where there is no visual indication that something went wrong- everything looks like it worked but you do not have a solid.

2. Local symmetry mode when manipulating points for surfaces with points visible. I was able to do it by mirroring the curves for half of the object and then seeing the loft result update, but I think that it would be really useful to have something more direct. You can get the most interesting shapes I've seen, using loft flow and point manipulation, it's a shame :)