This seems to be the transfer-window which determines our future defence, so it is crucial that we make the right choices. (The first good choice: "Forget Marquinhos" seems to be checked out right now).
I really hope we make the right choice with Lemos. There is a lot of options to be the loan-out, developing CB, but if we manage to land Umtiti, we should carefully asses who we should invest in, long term, and not just sign Lemos, because he is the least tricky to get and cheap.
We should ask ourself (I don't have all the answers):
Is he better than Meré, who is younger? Should we have closed the deal with Bailly instead (higher price, but more proven), together with Umtiti?
We could also go into betting mode, and maybe score the jackpot, if we somehow could get Andreas Christensen out of Chelsea's hands (and maintain his loan at Gladbach). That would certainly be worth a try, even though it looks hard (15-20M. would be a bargain for him, surely). Maybe we will get a chance next summer at the end of his loan if Chelsea is stupid enough to buy a starplayer instead of keeping him
The strategy with buying + loaning out a youngster is very wise, especially so a guy like Rodrigo Tarín from the B-team still can get a chance to be in the squad once in a while