At the dpkg level, this mostly works, yes. I can extract to e.g. ~/local, set $PATH, $LD_LIBRARY_PATH etc. and stuff works.
However, I'd also like to have some dependency resolution (ideally including already system-installed packages where possible, no need to install libc6 twice) and some more magic - for example, I have to manually adapt the file /etc/bash_completion if I want it to work out of ~/local, similarly, many programs only look at /etc/foo and not ~/local/etc/foo.
fakeroot doesn't really help and chroot again requires root privileges.
However, I'd also like to have some dependency resolution (ideally including already system-installed packages where possible, no need to install libc6 twice) and some more magic - for example, I have to manually adapt the file /etc/bash_completion if I want it to work out of ~/local, similarly, many programs only look at /etc/foo and not ~/local/etc/foo.
fakeroot doesn't really help and chroot again requires root privileges.
As I said, dreams :)