This is neglecting that the whole region in which Final Fantasy XII takes place is called Ivalice. It's unlikely that if the two were directly connected, they'd have a region named one thing and a country not too far away named the same.

If the worlds are connected directly, I'm sticking to the theory that they take place in different time periods. Afterall, airships are all over the place in FFXII, but they're considered ancient technology in FFT.

I don't think the Balthier we see in the Tactics remake will have anything to do with his alter-ego in FFXII. All I'm wondering is how they could possibly make him important to the plot without changing a lot of things (which would be a shame). The only way I thought they could get away with it was to replace Mustadio with Balthier.

As far as the note in the end of FFXII that makes reference to Bervenia, I'd imagine that has a lot more to do with Revenant Wings than anything else.