I actually have a Raspberry Pi coming tomorrow (Hopefully) and I plan to do almost the same setup. Though I agree that alot can be done with the Rasperry Pi, both it and the Pineapple have some hardware limitations. Also in combining them you don't eliminate a single point of failure but you do give yourself multiple means of access so you can diag if needbe.
Again, I haven't yet received my Pi and my opinion may change after it is setup.