Tips for providing multiple layouts in a multisite environment (aka the SaaS holy grail)

One of the apps I'm working on is a SaaS solution for an online product catalog. Every catalog has it's own domain and can be accessed as if it's a site on its own ( and are both served by the same Rails app).

Now building this app all works well, but I'm having some troubles thinking of a good solution for the templating system. Since these online catalogs are extending already existing websites of our clients it is needless to say that the templating system should be highly customizable.

There are a few solutions I have tried (and a few I've not), I'll share those with you and I'm interested with your solutions to this kind of problem.

1) Use the same erb templates for all catalogs, returning the same HTML structure for every catalog, but using a custom stylesheet per catalog. So turning the stylesheet plus images into metadata. Pro: easy to implement. Con: CSS is very limited to customize a layout. Con: The designer guy now hates me. Con: The CSS/images aren't in the same git repository, and you need to use something like FTP to update them.

2) Also turn everything under app/views into metadata. Pro: The sky is the limit Con: Hard to implement. Con: Hard to maintain. Con: You don't have custom controllers/actions (or models) for seperate pages and logic. Con: You quickly resort to ugly hacks because of the above reasons Con: Do I also need custom helpers per catelog? Are helpers metadata? Con: Templates are edited on a remote machine.

3) Use a different partial per html snippet per catalog. (haven't tried this yet)

4) Some kind of templating engine?

Any other ideas?

Recognizing the subdomain and doing the routing is really the easiest thing of a SaaS solution. But when you want to provide 'homepages' to clients through a SaaS solution, it's a lot tougher!