I agree: the "wants" can be a powerful motivating factor...
I'm more guilty of following my whims, rather than my needs: than just about anybody else in here...
Having said that: we're looking seriously at the "suitcase solar" kits from Samlex. It'll give us solar recharging capabilities that we can shuttle from the chassis to the house batteries as we see fit.
(MB Sprinter chassis: the two systems don't seem to tie together as easily as they do in other rigs...)