My feeling is that you are really overthinking this thing about your bike's wheels to the point of paranoia.

So far, how many kilometres have you done commuting on your bike since you've had the wheels that are on it now?

And what happens if one of your bike's wheels gives up and you pirate the one from the trailer? Where are you going to tote the stuff on the trailer? And do remember that if you are travelling, the trailer will add extra weight to your luggage which means you may exceed your allowances on some international and local flights. You will still need panniers to go on the Extra-Wheel anyway.

The three wheels also won't be interchangeable. As has been pointed out, the rear wheel dropout width is quite a lot more than the front. Tip[ of the day: Start looking more seriously at your bike and how it is put together, and see what the components are on there, and even start looking up on the Park Tools website for maintaining it.

Second-placed tip of the day: If you have any doubts about the wheels on your bike, invest the money you would spend on a trailer on upgrading the wheels.