That actually sounds like a great idea. I have usually used the tricot interfacing but your idea sounds really neat and less trouble. Any quilting could be done a block at a time and you could combine some smaller logos to make large blocks that would be the size of your larger tshirt motifs. Even plain shirts would be good because you could add an embroidery/applique or quilt design if you wish.
Some knits might be more difficult but maybe not. Since it is a block at a time, you could always set aside a block that might not work.
Have fun and keep us posted.
Kim