What are you trying to achieve by getting a 703? Did you inspect the one that was shipped to see if everything is okay?
As long as the shielding is installed (as indicated by the black circle on the box), then I don't see a reason why you'd keep exchanging until you get a 703. From what I'm reading, the 703s haven't fixed anything beyond the shielding problems. If I were you, I'd check that you've got:
* The black circle on the box (could also stick a WiFi router behind your screen, just to be sure)
* The external monitor case being in good condition
* Minimal backlight bleed
* Good colour uniformity
If you've got all of these things to a satisfactory level, then just hold on to it. You could easily keep exchanging to get a 703 which then has terrible backlight bleed, which is worse than not having the shielding installed from start of manufacturing IMHO.