[development] half sharing table in multisite

[sime]

Hi
I'm doing a multi-site install with 5 or 6 sites. These sites will be 
sharing every table except some obvious candidates like "system", 
"variable" and "cache".

I'm really looking for long-term maintainability, minimal patches, and 
so on. But I've yet to decide the best way manage data in the system and 
variable tables that is always going to be the same. For example, the 
system table will be duplicated because I want to have different themes 
installed and activated, however all of the installed modules are going 
to be exactly the same, and I will unfortunately be duplicating this 
other data. The same might goes for some variables.

I guess the manual way to manage this is, everytime I add/change a 
module setting, go into each installation and repeat the process so that 
all sites have the same configuration. Alternatively maybe I can set up 
a cron job to ensure that data cascades from a "master" installation to 
the other ones.

Any pointers/advice/warnings are appreciated. Especially book pages that 
I might have overlooked in my quest.

Thanks & Regards
Simon