I'm leaning towards giving Miz the ball and seeing what happens early tomorrow, for a couple reasons:
1 - If he's "on", he's the one arm with starting experience I have confidence in being able to keep the Cubs off the board in the 1st inning, and he'd have the best shot to give the Brewers any sort of length a couple times through the Cub batting order. It will be a highwire act - but will have much more to do with whether or not he's throwing strikes/locating that slider compared to whether or not he's keeping the ball in the park.
2 - If he's "on", the Brewers can get creative with their starting lineup without too much concern about guys getting put in strange defensive positions, in order to try and maximize offense. A high number of strikeouts and weak contact limit the damage that a less than GG caliber outfield is playing defense behind Miz if it means getting as many bats in the lineup as possible. Prioritize getting a damn lead early at home, then as the game moves on bring guys like Ortiz and Perkins off the bench for defense while playing with the lead. I wouldn't mind seeing Chourio as the DH and sticking Yelich (who at least isn't hobbled) in left - and Bauers in the other corner with Frelick in center.
Monasterio needs the start at short, find a way to get both Bauers and Vaughn in the lineup regardless of who the Cubs start (Imanaga's stuff should not prevent Bauers from starting, IMO), and stack the top of the order up in a way that doesn't stick hitters currently going through rough rally-killing slumps (looking at you Turang, Durbin, Ortiz) sandwiched between hitters that are reasonably dangerous.
Chourio LF/DH
Yelich DH/LF
Contreras C
Vaughn 1B
Bauers RF
Durbin 3B
Frelick CF
Mona SS
Turang 2B
I have zero faith Murphy is going to view this game the same way I do, but this would be my ideal lineup to start Saturday.