I said the same thing myself. We currently have the following U21 players who only qualify as A-list of which you can only have 17. This is because they haven't completed 2 years registration with the club - Gray, Bergvall, Odobert, Vuskovic, Yang, Tel. Additionally we have 4 association trained players - Spence, Solanke, Madds, Johnson. Buying another for the PL squad makes sense but you can only use 4 slots for AT players in UEFA rules.
So if you swap Wharton for Biss, it doesn't help us in Europe as he'd have go into the packed A-list. Gomes is the same. In fact Gomes would be club trained at Utd if he went back there. With a few of their's leaving, don't be surprised if they don't make a move for him.
I'll have to dig out the Ally Gold update.