My big thing with the FDX LOA was that they offered a rent subsidy in US Dollars!! I think for anyone working or living in the Euro zone would have to be PAID in EUROS!! And also have the living subsidy also in EUROS! Otherwise the hit in cost of living by being paid in Dollars (even at UPS wages) and living in Euros would be too much for average employee to stomach.
If they want to keep the pay rates and per diem based on the existing contract, then I think an extra cost of living stipend (for both rent and food) of at least $5000 per month (about 3300 Euros a month) would be a bare minimum to start.