Since this is a (much) needed item for the core of Ubercart, and no-one has been willing to step up to the plate to take the challenge, I would like to get some bids on what it would take to create a module that will combine the shipping costs of any type of shipping method applied to a product. As it stands, I am shipping through UPS and a freight company called Estes Express. Some products ship UPS, others ship Estes. I am yet to figure out a way to combine the UPS and Estes shipping rates into one single shipping calculation. I would personally like to see this module open sourced for the community and extensible enough that it will combine the shipping for ANY shipping method: UPS, FedEx, freight, Flat Rate, Weight Quote etc. yet not break the site if future core upgrades are applied... (meaning I don't wan't to have to edit any of the core files to make things work)
If you need more info on how our setup works, let me know.