How much would it cost to just pre-print 100 of them? You could always do an end of the year grab-bag of any that didn't sell (like woot.com's woot-offs).
You'd probably not come out ahead on all designs, but I'm sure people paying $100 for the shirt would love to have it asap.
Then no one could choose a size. It's a tough printing job any way you slice it. Perhaps doing it in house would be a little faster, but that takes a lot of time and money.
You'd probably not come out ahead on all designs, but I'm sure people paying $100 for the shirt would love to have it asap.