So when Soroka is ready how do the Braves handle it. 
Elder gets sent down or to the pen-- not sure you want a guy who has shown success in the pen.
Soroka to the pen--  he could be our Britton, but BP put stress on a fragile body.. plus he is ace level when right
Morton to pen--  I love this idea personally, but I doubt Morton wants to do that.  I think I read somewhere that he goes home after his start to be with family for a few days.  
6 man rotation-- another great idea, but does that put too much stress on the pen since Elder/Strider/Morton/and probably Soroka can't go deep into games.  You would be one short in the pen with a 6 man rotation
piggy back guys --  I don't think anyone has tried this, and not sure how it affects arms, but guys going for 40-50 pitches, then your piggy back comes in.   I doubt any starter would want to do that since that is not what they are used to, but I love the idea of Strider coming in after Elder.. Or Soroka  after Morton...   This is very off the wall, not going to happen idea.  
Usually these things find a way to work themselves out, but I would probably bet Elder gets optioned over Elder to the pen if everyone is healthy.