In addition to Get-DrsRecommendation, I think it would be useful to have a cmdlet to Get -SDRSRecommendation. It would be nice to be able to specify -Type 'Space' or 'Performance' or something to indicate whether you want recommendations based on space balancing or performance (IO) balancing.
However, in addition to simply providing the current set of recommendations for balancing the overall DSCs, it would be nice if we could specify a proposed disk size and get a recommendation for the best datastore to place it on - perhaps using the Space Threshold property as a limit (since sometimes sheer size available alone is not the best indicator of the best destination).