Basically, it would act like a virtual marketplace where the currency is Energy and Metal, and the stock are units and other such confectioneries.
It would allow players to buy units from one another from set amounts of energy or metal specified by the players. You would be able to haggle over how much metal for a T2 Con or sell Atlas's for 50 M a pop.
You could add options such as bidding or auctioning units and the highest price buys the unit. The possibilities are pretty wide.
It would of course only work with other ally players with the same widget, and shouldn't affect gameplay too much apart from increasing team play and community spirit!

It could replace the 'H' menu which not many people use any more with the arrival of more efficient widgets to achieve the same functions.
As I said, this isn't a request, and I don't expect anybody to actually make something like this as it would probably require quite a bit of coding. Regardless, I may even come back to this in the future if I decide to further my Lua knowledges.
And remember kids, sharing is fun!