We boondock almost exclusively, and I use our microwave for storage of disposable plates, bowls, forks, spoons, knives, and napkins. It has a latchable door and is perfect for this function.
However we have already installed substantial solar
and are in the process of a corresponding lithium upgrade as well, and my husband is hell-bent on being able to use the microwave for its original intended purpose - to warm food. In his view, it's far more efficient to use a microwave than a gas stove when potable water and wastewater tank space are both precious commodities. Eliminating the need to wash pots and pans will help in that regard. So our lithium system is being sized partly with this consideration in mind.
Possible moral of this story - lithium is not yet mainstream but it will get there, and whatever you do to your cabinetry, you might want to preserve the ability to put your microwave back in at some future point, either for your own purposes or for resale value.