In my imaginary space-universe, the UFP employs Astrotrains: multi-linked transport tugs. One main hull like this (a Command Hull) and up to four container sections, all interconnected down the X-axis centerline via special support frames and each container carrying its own Warp Sustainer Module. One-four, one-four, one-four.
This specific design rendered here could haul Tri-Pods: three containers arranged in an inverse Equilateral config. It would need an extra nacelle to haul the Quad-Pod config. Most Starfleet Astrotrains would be deployed under the auspices of Starfleet Quartermaster Command.

Good idea. If you want, I can make a tri-nacelle version for you. Would need a different class name though.

I would go with the Challenger Class nomenclature for the tri-warp config. Not named after the Space Shuttle, but after this:
http://www.youtube.com/watch?v=XhgHrDbN4EU

Agh! Hit Add Reply too soon.
If you want to render a Challenger Heavy Tug hull, be sure to bulk up the impulse deck a bit as well (i.e., more indicative hull features on the dorsal view).

http://www.furaffinity.net/view/12598964/

Or Indiana Jones?