How about just going with the items in your first post that started the thread? I think that is a pretty good list of features to start with and something I would certainly be happy with. As things progressed the idea of possibly of adding more capability to the original board could be entertained and the board could be expanded if things develop? Since I am no circuit designer, some of the original items you suggested may even prove to be difficult or too much for the initial board design? Some of us (me for sure) can really come up with the features, but also have no idea what is involved in creating a circuit to make it happen. Reference to your signature line once again comes to mind...
But I really do get that part of it! 
One other thing, these boards could be used as a starting point for us 'prototypically challenged' folks that are not really sure how all these signals work together anyway? They would not have to 'do everything for everyone'. We could upgrade to the already available stuff for more advanced signaling, etc. as we go along. Maybe sort of a starting and learning point or starting to learn so to speak? Some would probably end up being good with what they had and others may want to go to more advanced methods?
