I’d have the upgrade done and then enjoy the motorhome as much as possible because the next compact MH may not be available as a diesel.
Diesels are becoming more difficult to justify, and when demand gets low enough manufacturers will pull the plug. Objectively there are too many issues not worth the trouble for lighter vehicles.
RAM quit building diesel ProMaster years ago, and Ford suspended introduction of the “new” diesel Transit two years ago, so how long will Mercedes find it viable? I would bet that if Mercedes had a good truck-ready gas engine, they would already be offering it on Sprinter Cutaways. Future looks bleak for smaller diesels in my opinion, so enjoy while you can.