I would rather see Rooney go and be sold to another club. What Man United needs is a good holding midfielder to partner with Pogba. Pogba is very aggressive and offensive minded, I think Blind was played as a holding midfielder before at Ajax and has flourished in the position. So why not place him there when Luke Shaw gets back from injury.
I completely agree with your opinion, seems you can read my mind lol. Actually Schneiderlin is suitable to be partnered with Pogba, but Schneiderlin still hasnt found his best performance until now. So, among the current midfielders Man United have, Blind is the best option.
Imo there are too many players who getting their position changed in Man United squad. E.g: Rooney (Striker -> midfielder), Blind (defensive midfielder -> center back), Valencia (winger -> full back), carrick (defensive midfielder -> center back sometimes), and Rojo (full back -> center back). Sometimes it works but not for every match.
In the case of Blind and Valencia, I think they are doing well in their new positions, but in the center back position I still prefer Smalling to be partnered with Bailley. I like Blind better than Shaw at left back because Blind also played the position at Ajax. I think he played three positions over there, CB, LB and DM. And has played them well through the years.
Herrera is doing a decent job as defensive midfielder as we have recently seen in the game vs Liverpool. I hope to see him play more in that position.