I was working on a low-cost DIY display design just like this for my Comet, but ran out of time and ended up getting xpin displays. You put this out with boards and everything. Very nice work! Great idea making a kit.
I've seen tons of inexpensive numeric LED displays on eBay and whatnot (that is where I got mine from), but couldn't easily track down Alpha-numeric ones. Have you been able to source those?