For me subcomponent edits would be a significant step up for MoI - kind of thing you have in Rhino, when you can select a for example one of the surfaces of the box (ctrl+shift subcomponent select), scale it and all connected surfaces will update as well.
Well and also linux support would be great as my main workstation is Linux based - even semi official / not fully supported option would work. It could even be a "simple" WINE wrap + let's say appimage / flatpak for cross distro compatibility ( I use quotes as personally I have one problem with wine and MoI I've been unable to sort out).