Have you considered a Symbian device - Nokia E7 perhaps. they have full official MS office support now. great battery life and full-on multitasking. With the Belle update which arrived a couple of months ago they are very nice and bang upto date graphically. Despite Elop's best efforts they will be around and supports for another couple of years at least

at the end of the day though, if you absolutley need XY and Z apps, and they only run on iOS or Android, then you are stuck.