I'd like to be able to edit shields in PCS2 (that's pretty much the only reason I still use Modelview).
Modelview also has another interesting feature, converting missile banks to guns and the other way around.
That would also come in handy from time to time, doing it "by hand" is boring and involves a lot of copypasting.
As for bugfixes, PCS2 sometimes takes cursor out of the text box I'd like to edit, it becomes a bit frustrating to have it suddenly do that in the middle of writing (if I move the mouse, cursor returns, but sometimes it happen a few times in a row).