Hi there
I really appreciate what you are trying to do for your mother in law, and it would seem to be a good idea for all of you to share the burden of care and have time off in between.
But unfortunately, it is most common for people with dementia to be confused and disorientated at the best of times, even within their own homes. With your mother in law being in the middle stages, you may have found already that this is the case, and Im afraid if this is so, then I doubt that this idea will have a good impact on your mother in laws behaviour and so will have quite a negative impact on your family.
This is just my opinion which i believe you asked for....
Thats not to say that it wont work. It may very successfully, you can only try it.
But please be aware that she may appear more confused than she really (Medically) is because of all the moving around.
Within my work i witness lots of ppl disorientated and wanting to go home, even though they are at home, but you ask them to take you to a particular room and they can. That familiarity is
there, and I dont think your mother in law will have time to build upon any thing like familiarity.
As for you other options.. Im afraid that only leaves the obvious.
Please do let us know how you get on.