Remove both unity and gnome?
Solution 1:
You can create a standalone compiz session with gnome3-gnome-panel+metacity, unity 2d launcher, awn wing-panel(with all applets), docky, synypse, cairo-dock,slingshot or combination of these.Have a look on following screenshots:
Edgebuntu Desktop
Milky-Moorhen (DE)
Cairo-Dock Session
Unity Gnome-shell fusion
In above screenshots you can replace unity-launcher with docky or awn or cairo-dock.
To setup custom sssion with compiz check out this article:
http://www.webupd8.org/2012/02/how-to-create-standalone-compiz-session.html
For Awn-Wingpanel checkout this video:
http://vimeo.com/18598545
For Ciaro-dock 2.4 with custom gnome-session follow this article:
http://www.webupd8.org/2011/09/cairo-dock-240-released-with-custom.html
You can get additional help from these articles:
[HOWTO] Configure Unity 2D to Simulate Unity 3D
How to enable compiz in gnome-classic mode
Fix gnome-panel in gnome fallback session
Run AWN / Dock in Natty Narwhal(generally for gnome2)
Notes: There are many bugs in 11.10, which makes using custom session a painful experience(such as this bug: #bug 826771).I will update the post with important GDM & compiz fix.
Updates: Bug 826771 has been fixed in nautilus - 1:3.2.1-0ubuntu4.2 (ubuntu 12.04) for gnome-session.But there are other bugs (specially gdm bugs) still present in Ubuntu 12.04.
Solution 2:
For the first question:
apt-get purge gnome
apt-get autoremove
More info at here: Remove Gnome Shell completely after installing it?
For Unity:
apt-get remove unity unity-2d-places unity-2d unity-2d-panel unity-2d-spread unity-asset-pool unity-services unity-lens-files unity-lens-music unity-lens-applications gir1.2-unity-4.0 unity-common indicator-sound indicator-power indicator-appmenu libindicator6 indicator-application evolution-indicator indicator-datetime indicator-messages libnux-1.0-0 nuxtools
More info here: Remove Gnome Shell completely after installing it?
There's a lot of info already if people took the time to do a fast search in here
Solution 3:
Install Xubuntu-desktop
sudo apt-get install xubuntu-desktop
its the best alternative for people who hates unity and Gnome . and one more thing you can run compiz in xubuntu also .
Solution 4:
I'm not sure if this qualifies as an answer, but I hope it's OK to put it here, as it may be too big for a comment. I haven't actually tried getting rid of the shell - I use gnome3 "Classic", with AWN and Compiz. I actually like having the Gnome panel at the top with some of its apps and indicators, but then I have dual monitors, so I have room for an extra panel. I have AWN on the bottom, and use it a bit like the Unity panel.
Your idea sounded interesting, so I looked around a little and found this article in the arch wiki that might be interesting to you:
https://wiki.archlinux.org/index.php/Compiz
About half-way down is the section "As a Standalone Window Manager" that you might want to look at.