Rails - Nov 2005 - Meta-routing: How to keep individual domains(urls) when rewriting an app as a shared service?

Hi all,

Context:
----------------
A client asked me to rewrite its site. It''s basically 2 times the same 
set of features.
    <theirdomain>.com/index
    <theirdomain>.com/group1/***
    <theirdomain>.com/group2/***

I feel I could generify it enough to host it and resell it, à-la BackPack.
  => on my server :
      1 rails-app
      1 DB with all the accounts data
      each account  can be customized (logo, css).


ZE Problem : the urls/domains
-----------------
* they want to keep their current domain and urls system


In other words:
   - the urls must not reflect the shared service
, and
   - they DON''T WANT
          www.ABCD.com/index
     to become
          www.mysharedservice.com/ABCD/index


Question :
-----------------
Q1/ is this doable?

If it is
Q2/ what is required in the app, and on the main server to solve this 
meta-routing problem.



Thanks in advance.

Alain Ravet