I'm surprised people think Ronaldo is an issue. If Ronaldo doesn't like playing less then he's going to have to get a grip and realise he's not superman. He has been over his career, but even he is not immune to age. He needs a rest, and he needs support. He'll still be key but it is part of the new managers job to set boundaries, even for Ronaldo.
So what do you do, sign somebody happy to sit on a bench all year because he's utterly mediocre, wasting resources in the process and leaving us scratching our head in a years time?
Or more sensibly, do you identify a long term option that gives us depth and quality? If Nunez is that man you go and get him. I have no idea if he is as I think that requires proper scouting, but if the right man is available this summer we must get him because our forward line and sources of goals are worrying.