Pre cut pieces sound like a good idea in principle but unless you are using an accu cut machine there is a big variation in types of rulers, marking pencils and hand/eye coordination of the quilter to get accurate blocks. Over the years, I have purchased kits or exchanged kits and found it was a headache. But on the other hand, if the finished block size is flexible, it would be fun getting different fabric units to play with.
Moosegirl