I think the Wiemer discussion really is a non-issue. If he makes the OD roster and needs to be sent down for two weeks later in the season to preserve a year of control, I find it highly unlikely there's any scenario that prevents the FO from doing so. Right now, it seems to make most sense to do it when Taylor comes back, but it's a loong season, I'm sure there will be ample opportunity to do so later if he's mashing or there are injuries, etc.
But even in those two cases 1.) as others have noted, replacing a hot rookie for 2 weeks with another capable player isn't likely to cost many, if any, wins, and 2.) we have many, many other options to fill in for injuries for a couple weeks (possibly Anderson, Winker, and Miller on the big league roster already, plus Frelick, Perkins, possibly Naquin still, even Turang, and a whole host of other minor league guys, including even Chourio at some point, that could have a cup of coffee until Wiemer can come back up).