Nobody is going to take our microwave out of any of our RV's nor the propane oven. Not only extra storage may be had somewhat when on the road, but can't use the appliance if it's not there when desired for use.
Having a convection oven/microwave combo unit solves both the extra storage and having both an oven and a microwave too. Runs great off a battery bank with a 1500 watt or larger inverter or a 1500 watt or larger generator which are both simply great for so many other things usage needs/desires. We have both the generator and an inverter in our RV's and if revising to an combo micro/convection unit would thus have the best of all scenarios as there's also always the propane range.
2500 watt inverter with 5 group 31 deep cycle batteries and a 2000 watt EU 2000 Honda generator in the 5th wheel.
1500 watt inverter with 3 group 31 deep cycle batteries and a 3400 watt built in propane generator with our TC's two 30# PP tanks in our big Lance truck camper.
Had a 2000 watt inverter with 4 group 31 deep cycle batteries and simply moved the Honda generator to the TT as it's portable and so is our 6 gallon aux gasoline long run supply tank.
Our motorhomes always had both the inverter with a battery bank and a built in generator too as why not?
Always had and have full use of everything in the our RV's by our having plenty of propane and gasoline or diesel no matter where we happen to stop for a just a few hours or even days and external hookups not ever needed as our RV's always had and have liquid tanks too and are truly "Self-Contained" not wishfully so! Again, why not? Aren't you and yours worth the real comfort and convenience?