Nima - you are right in stating the problems that exist should subsites work, however, I don't think they can in any event.
Janine - I missed the obvious! Different instances would present the same communities with different presentation, so that would not be much use unless you started a very messy filtering process - I don't think I'll go there!!
You mention themes, but I guess you mean designs as opposed to the actual .LRN themes, as they only go a little way to providing a custom look.
If people are interested in our solution, I'll gladly provide details. It's not ideal for 2 reasons:
- It involves a change to template_tag in the templating handler, which seems fairly core stuff
- The templating cache has to be refreshed constantly because I could not find another way around a problem where the master template would be cached from page to page, even if it had changed. Obviously this change is detremental to performance, although I'm not certain to what degree.
The second issue is probably resolvable if someone with more experience looked at what was going on - in the end I got it to work and we are living with the performance hit.
The first issue is only significant if this was a feature people wanted in core .LRN, so I guess it would be down to whether this was put forward as a TIP.