OK, here's my take on it :-) I am in the process of installing the two tank system in my 1983 240D Benz and I also brew my own biodiesel in a system that I also expanding for double capacity production.
I live in a climate that is cold and in winter it gets stinkin' cold, so the plan is to start/stop on dino (in the cold) and then run BD in the hot tank. This, IMHO, solves the "what to do with cold weather BD use" question. Biodiesel falshes at around 300F so the heat isn't a safety concern. I could also go the WVO route in summer with BD as the start/stop fuel or run both tanks on B100.
My set up will have a heat exchanger in the engine bay, as well as heated lines to and from the tank (HoH) and a coil of copper tubing inside the second tank. The one in the engine bay is hose in hose just before the IP and flushes each time the flip over is done IE: both dino/BD and WVO run through it just before the IP. An extra in-line fuel filter is also in the plans, as well as a sender that will give me a fuel gauge for the hot tank.
For both the sender and in-line filter:
http://www.marinegeneral.com/acatalog/Online_Catalog_Fuel_Filters_Water_Separators___Senders___Misc__347.html
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