Rumours say that he has a 10m release clause. Would not think twice, sell Wague with a buy-back option to Getafe if possible (I still rate him) and give TE a first-team chance. It is quite hard to find a talented fullback with good physical profile. And, of course, move Roberto to the midfield and sell both Busquets and Rakitic.
Sadly won't ever happen. And even Raki might stick around until his contract expires.
I know we wanted Benfica's Tavares last summer but were we ever rumoured to be interested in Esteves? Sure for 10m he would be worth an investment but I cuold see him prefering to join a club like Dortmund (with Achraf going back to Madrid) where he could get immediate first team experience instead of coming here. Porto will probably also do everything in their power to convince him to renew his contract with a higher or no release clause.
But if we were somehow able to buy Esteves I would prefer to get Emerson back from loan and send TE to Betis. Wague's future at the club is probably done but we should still keep him under a club control by using a buy-back clause (like you suggested) just in case he'll suddenly "explode" in another club. Don't know if we'll really find the right club for him on the last day of the winter transfer window though.
Also, we'll have to make a decision about Semedo this summer. Do we still see him as a part of our future or do we sell him if we get an offer of around 30-40m? And if we sell him, who will be our starter next year? I think this is our last chance to sell Semedo for that much. If he'd have another average season and with only a year left on his contract we would probably only get 20m or so if we decide to sell him in 2021. I get a feeling many people here still consider him as a young player but forget he'll be 27 this year so he's far from someone who we should wait forever to show he's good enough. He'll get at least 3 full seasons at the club, most players similar to him don't get that much time. I don't hate him, I just think he is what we see in most games at this point of his career and with not much room for improvement. A serviceable player who could still stay for a year with our more urgent needs in other positions but shouldnt' be unquestionable starter and we should seriously consider replacing him longterm.
BTW, watching Esteves's highlights video I like him overall but dislike him dribbling/running through the middle so much (unless he has played as a RM/CM in those games). This won't work at the top level.
[youtube]ICL0NsUh9uM[/youtube]