"The converter itself would have to have adjustable parameters for the remote or BT to be able to change, so you couldn't just add one of these to your old converter"
Hmmmm. My Renogy DC-DC charger has a buck/boost converter in it and DIP switches for various settings and charging profiles for various battery types (limited choices however)
What if the gizmo being invented right here :) could be added to your old converter that is doing say 13.8v and you had remote or BT to adjust your added new gizmo's not so limited choice of parameters ? No new converter needed!