McCutchen should be playing LF against LHP and Yelich should be sitting. The only problem with this then is that Hiura would have to be the DH against LHP. I would be fine with this as I don't believe in the reverse splits for Hiura it just doesn't make any logical sense at all.
Also the Brewers really don't have another RH bat with Brosseau possibly being hurt to put in the lineup against a LHP. Tellez is another problem but less so against LHP. The Brewers really needed another RH bat to hit against LHP and with Brosseau possibly being out that may cause some more issues against LHP. So Hiura is going to have to face LHP reverse splits or no reverse splits.
Against RHP I would just play matchup and get McCutchen some days in LF when Yelich needs a day off and at DH if Hiura looks to be slipping at all. At smaller parks like in Cincinnati I would put McCutchen in CF but no way he should be playing in CF where there needs to be a lot of ground covered. Yelich is bad enough in LF and Renfroe should really be playing LF and not RF.
The problem is that Yelich has turned into a ground ball machine against LHP. Nearly every zone against LHP for Yelich is at a negative launch angle so the ball is just going straight into the ground.