US Airways Dividend Miles - Unclear using e-upgrades

I am a bit puzzeled about the use of e-upgrades when flying transatlantic flights. Is it possible to purchase upgrades from say, V class to Q class so one can then upgrade using DM's to advance to Envoy?
Can one do that on the Return Trip, having flown half of the V class ticket?

I am flying FRA to PHL, then CLT to FRA a month later.

E-upgrades are not valid on TA flights.

From US website:
E-Upgrades are a fast and easy way for Dividend Miles members to upgrade on US Airways operated flights within the continental U.S., Alaska, Bermuda, Canada, Central America, the Caribbean and Mexico.

I am a bit puzzeled about the use of e-upgrades when flying transatlantic flights. Is it possible to purchase upgrades from say, V class to Q class so one can then upgrade using DM's to advance to Envoy?
Can one do that on the Return Trip, having flown half of the V class ticket?

I am flying FRA to PHL, then CLT to FRA a month later.

I would contact US Airways Reservations (Silver, Gold or CHP, if you are Preferred) and ask how much it would cost to pay the difference in your fare to a M, H or Q fare. Before changing your ticket & paying the difference, have them make sure Envoy upgrade seats are available. If so, they should be able to collect the money, upgrade your seats & deduct the miles from your account (30K each direction) in one phone call.