Here's a tough request, but it's what I'm trying to collect, so I'll give it a shot.
Is there any chance we could get an All-Century Team nominees registry set?
Here's the list of the 100 nominees: http://mlb.mlb.com/mlb/history/mlb_history_moreinfo.jsp
Essentially any graded card of the 100 nominees would count and the registry set would be 'complete' when all 100 were represented.
No problem if it's too complicated!