I think I have brought his up before but it has been a while. WPMU Domain Mapping is great and is one of the main plugins I use.
There is a plugin which provided a really powerful ability that I would like to use. The developer has stopped updating it though.
I would like to suggest the this functionality be added to WPMU's Domain Mapping Plugin. In the meantime if someone could possibly look at the code for DMS (Domain Mapping System) and recommend how I might modify WPMU's Domain mapping to map to pages in one networks site I would really appreciate it.