You're correct. The older ones were noisier and smellier, but for towing they can't be beat. The new ones are a LOT quieter, some brands quieter than others (Chevy is quieter than Dodge). You have the idea, but I don't think using that tank for a recepticle would help things any. The computer might not like it.

Dad has had a diesel car or truck since 1973, my first one was a 1986 6.2 Suburban.