Like for example I have a Rogers (Canada) phone. Then comes 4.3 rollout for let's say Sprint (USA). I can use the sachesi program undertakes on my laptop then update my phone with the sprint 4.3 by just putting in the type of my phone and the country code and carrier code of the carrier with the update
I don't know if there's an app that does that, but if you root your phone, then load the (Sprint) rom, that'll do what you're looking for. There are many resources on rooting & roming.