For this season, why not?
The team is in desperate need to get more offense in there. If that's by plugging Burger (or anyone else) at 3B and moving Mocada to 2B, then go do it.
It's no like we're relocating Mike Schmidt here.
Nothing is owed to Moncada. If the Sox feel they can find a good enough bat to plug in at 3B and move Moncada to 2B, Sox need to explore every option.