Heh. I'm sure that Diablo5 is certainly deserves its own thread
Thread hi-jacking is bad mostly because few people would expect to find anything interesting in topic if main topic theme isn't interesting to them. So, Kroll, you will receive even more valueable feedback if you create standalone theme for Diablo5

Yes, it is pretty safe while you do things in right order:
1. Install theme
2. Select it in desktop menu
3. REBOOT
4. Test it and post feedback to Kroll
5. *** Unselect Diablo5 in desktop menu ***
6. Remove package
7. REBOOT

It will revert left desktop panel back after removing package and rebooting

Btw, i found that i forgot to add line removing /usr/share/applications/hildon-status-bar/applications-menu.desktop in prerm script of Diablo5's deb package. So, applications menu applet will not disappear from status bar after removing the theme. You can remove this file by your hands after removing the package.