The embroidery part of your plan use open designs, thick/ heavy thread designs probably won't work so well. Use some ( scrap) tshirt fabric for a practice to see how it goes & work out the ( bugs) before working on the quilt pieces. T- shirts don't ( rag) well. That part of the plan probably isn't going to work. Especially if using t- shirt fabric on the back too. You could put cotton sashing strips around the t- shirt blocks to frame them and rag that, but you need cotton, regular or flannel ( best for raggy) on the back.