1)So i'd be ok using that MPI as a PWO drink?
absolutely.
2) would it be better as a PWO if i made the mix 85 (MPI)/15 Whey concentrate?
splitting hairs.
3) That mix would also be good before bed wouldnt it?
absolutely.
4) have you added any flavour to your batch in the past? The product description for MPI makes it seem like itd have a funny taste, i was thinking of maybe adding chocolate? (producing a quasi chocolate milk?)
I add flavor to every batch. You cant go wrong with any TrueProtein premium flavor (except chocolate banana; its great at first, but gets old after a while. Everyone else seems to love it though.) The Premium dutch chocolate is ridiculously good, and obviously even better when mixed with milk. To be honest I cant tell any difference tastewise between the ion-exchange isolate i used to use and MPI. The powder is a different consistency when dry, and some batches of MPI clump a little when mixed, but other than that, i cant discern any difference.
5) I like the idea of MPI as it seems to be more versatile than straight whey... if im wrong let me know... what is the typical expirary date on MPI is buyin 10 lbs too much?
no clue honestly, but like Easto said, if its dry and stored like every other quasi-perishable item, i dont see it going bad anytime in the next few years