[gb2world]

Hi Ashley -

How about this approach:
1 - Start out with a css reset
2 - Strip out all css associated with modules and addons to their own unique file. So any css associated with a module which can be enabled or disabled in the administration's module page has its own css file. (FLC is treated as an addon - not its own css file.)
3 - The individual css files are enabled/disabled in css_service.tpl depending upon if the module is enabled or disabled in the cart.
4 - The cleaned up reset/main.css file is loaded first - at the top of the cascade
5 - The module css files are loaded next
6 - Any required skin/template css file is cascaded on top after that
7 - A clean css is loaded where the individual designers can add their own css if they want to minimize changes to your standard files.
8 - When the site goes into production mode - an addon that aggregates and compresses the css files is applied (or you have to do it manually)
9 - Browser adjusted css files are cascaded last based on the browser in play - I am not sure if these can be aggregated since they are loaded at run time based on the browser - but they can at least be compressed. (Should not be too big anyway)

10 - To debug - you have the ability to go back and load the original css files

(I think this is close to Balinor's method - except that maybe the aggregation and compression could be added to the flow.)