Have been trying to figure out the best way to have a sub-domain with a lot of different routes that are specific to just that sub-domain... Some examples (vBulletin based):
Our tools section: http://tools.digitalpoint.com/ 19 different tools, some of which are very complex (like our keyword tracker).
Digital Point Ads: http://advertising.digitalpoint.com/ Probably going to end up with about 10-15 routes depending on how I set it up within XF.
I imagine some will want to put the resource manager on it's own sub-domain when it's available, so it would need it's own index prefix for it's route.
Then you could just have an index.php file with a unique Dependency class for the sub-domain.