We have the exact same floorplan.
I cannot see any advantage to removing a MW and then hiding the open space with a blank piece of plastic. At the very least I'd have hinged it to allow storage of paper plates/towels/etc.
Although we don't use it often, our Convection/MW has baked cookies, jalapeno poppers, warmed drinks, popped popcorn, etc., and has done so without heating up the rest of the AS. Of course it requires shore power or generator but we usually have one or the other available if only for the purpose (in the case of the gen.)
While camping at Lake Catherine last July a big storm blew in and shut down the entire area from power. Although planning for shore power...(we were on a long trip which included some boondocking so had our gen with us).... our generator powered our AC, MW, and wife's hair dryer... and our neighbors plugged into it momentarily to take advantage for their needs. (They had failed to bring their gen because they expected shore power at the campsite.)
Anyway, although this is about removing a MW, I'd suggest you try using it and you might find how useful it can be.
Meanwhile,.... it's easy to remove. Four screws on the ventilated cover and pull it out. (In fact, that's why some folks enjoy the experience of it falling out...it's improperly secured by AS.) Firstly, the MW sits on a shelf which is cantilevered and not supported at the rear.
I cut a 2x4 down to a 2x3 and laid it beneath the rear of the shelf, and secured it to the shelf with a couple of deck screws. Now it doesn't bounce-around. I also screwed down a long strip of 1x1 along the front, just in front of the MW front legs, so it cannot "hop" out of the shelf. (The flimsy sheet metal cover is the only thing to prevent that otherwise.) Now the MW rides securely, and it's easy to pop frozen sausage/biscuits into the MW for a quick breakfast and get on down the road, or go explore.
Hope this helps.