That's the way I'd would (and do w/my little low tech cms).
I use a version of
http://dev.rubyonrails.org/svn/rails/plugins/account_location/lib/account_location.rb
and just grab the current site given it's host. The way I handle it is
all sites have a subdomain like
username.cms.com but the site can also
be domained - that is
usernames-site.com. Domaining in this way has
been a big plus for me.
The set up in apache is cake also. I just wildcard the *.
cms.com
domain and make sure the cms is the 'default' site in apache (if I
remember right by making it first or last in the alphabet in hosts/
enabled-sites) this way all the sites are feed thru there if they
don't have their own .conf file. Probably not best practice but works
pretty good for me.
The other thing I do, which probably is not done for some good reason
in other better cms's, is keeping my styles and layouts in the db -
and just assume that more than one domain is going to be supported.
This way I can just copy whole sites - layout (using liquid), style,
and pages in one or two clicks. Very handy. ( and cache the css)
I sure do like the use of engines. They make great since but I'm still
getting my feet under me understanding for example how to 'build your
site within adva-cms' but I've not looked around enough yet to have a
good question but things look real appealing so far, great job to all.