re: WFFBBDL (critical info in OP this is dynasty baseball)
I don't like the idea of having to through back prospects at the end of every season. Yeah, ESPN has problems with minor leaguers, but maybe because when I had Duffy, Miller, and Yelich on my team, they were all in A ball still and I was sitting on them for a couple years.
You don't have to throw guys back, you have the option. I guess we could do it this way though:
Option A) Move prospect to main roster and drop a guy
Optiom B) Retain prospect and they become your 1st rd pick in supplemental draft (and each round after if you keep more than 1 prospect)
Option C: CUT prospect