Interesting timing: just two days ago, I spent a good part of my afternoon making "emacs -nw" running inside GNU screen to look more or less exactly the way my standard windowed Emacs looks. That included mostly fiddling with terminal settings and finding colors that are supported by the terminal and resemble my original choices (and some other tweaking here and there). Now clickong on my Emacs icon on the desktop wi…
I use a similar setup with urxvt and stumpwm. In stumpwm I have ;; Launch emacs (defcommand emacs () () (run-or-raise "urxvt -title emacs -e screen -U -dRR -S emacs -c ~/.screenrc.emacs" '(:title "emacs" :instance "urxvt" :class "URxvt"))) which will launch emacs (or raise it if it was already launched). Some of the thing you might want to consider when doing "emacs -nw" - Make sure your TERM is exported appropriatly…
gnome-terminal -x /bin/bash -c /usr/bin/screen
gnome-terminal -x /usr/bin/screen
Copy/Paste works fine for me in so far as that is one of the few things I use the mouse for. (I guess, in a lot of case you use the mouse anyway to select the text you'd like to copy.)
Remapping some keys is indeed necessary. In particular, GNU screen's standard escape key sequence is C-a, which in Emacs a lot of people probably prefer to be bound to (move-beginning-of-line). But also within Emacs some keys may need to be bound using input-decode-map.
As for your launcher, one thing I did differently is that my start script does not automatically re-attach to a detached screen session, but will show me a dialog window where I can select the one thing or the other. The reason for this is that I often keep a few Emacsen running in parallel for a long time, each of which is dedicated to a different aspect of my work. If I detach one session it is not always the case that I want to continue there the next time I open a new Emacs. Also, if more than one Emacs is detached I'd like to be able to say which one I want to re-attach to.
I looked at wanderlust a few years ago when I was looking for an IMAP-compatible email client for Emacs but in the end I wasn't convinced by it. Can't remember, though, what I didn't like about it, perhaps I should give it another chance.