The goal would be to improve player experience but also create more consistency. Choosing specific mercs that can’t be spammed could confuse players more and doesn’t match up with any way DB is being played. Should be all in or not at all IMO. As stated in the OP - there should still be a place for trying new mercs, Vas stacks, and melee only. I just think it should be separated a bit to provide better matches to the players that want them and grow the ranked/comp playerbase.
From the CMM test it seems players do want a 1-merc limit at least in ranked so maybe SD will do something with that feedback.