Mike...sounds like things are pretty well thought out already! As to the purifier...even though you are making RO...
1. You are putting it in tanks and running it through plastic piping which can add "flavor"!
2. I've also been on some boats using RO and found that the water has a bit of funny taste to it...don't claim this WILL happen but maybe there's something thatcan happen as system ages or filters aren't kept up or something.
Anyway, a small sink filter...like a PUR undersink filter
leaves you with GREAT water for your Coffee! BTW... Sam's Club sells Starbucks beans in 2LB bgs when you decide to provision! (We loaded 64 bags for our trip!...that's why I really got rid of the bow thruster...to make room for the coffee!)