Well, possible issue I found - apparently the 8735 does not have a removable/changeable converter separate from the distribution panel. It sounds like the whole unit would need to be replaced (option 1).
Option 2 - I found some references of people in the same predicament just mounting a stand-alone converter of their choosing as a remote battery charger. Several on Amazon come wired up with a 110 15a plug. Seems like it could be mounted in the front compartment and wired up with a very short run of heavy guage wire. If I did this, I’d build a little panel with room for a future charge controller. Definitely easy and un-doable but kind of ghetto (although I’m sure my work would be better than factory). Just use the factory plug-in if on shore power and only use the remote converter if charging while boondocking (and maybe have my batts on a higher quality charger at home).
I’ll confirm this is my situation and think about it. If I changed the whole factory distribution panel/converter, I’d probably want to increase the wire size to the batteries. Could turn into a big project...