Have you read through k9Sprinter's thread on his Dobervann? He has three 8D batteries and lots of solar to power the AC for his dogs. I don't remember what else he has in terms of alternator/generator capacity, inverters, shore powered re-chargers, etc. though I do know a Sprinter can run two high capacity alternators simultaneously. He also has a thread on the Sprinter-Source forum. You might try to contact him via p.m. or email for direct info.
Could adding more battery capacity and recharging from shore power when you aren't on the road be a possibility? What about adding a 2nd alternator (I think I have read that quite a few domestic vans have an available spot for one.)
viewtopic.php?f=15&t=5616
http://sprinter-source.com/forum/showthread.php?t=13275