As Fisherking said, giving a neighboring province to Persia seems likely to just lead to Persia declaring war on you.

This is another reason why I like GB.
A) As an island, the home provinces do not share a land border with anyone.
B) As a naval power, it's well positioned to earn money through trade, which lessens the need for large land holdings to generate income
C) I can capture many islands (particularly in the Carribean) that generate trade goods and don't share any land borders

I'm running a GB campaign right now where I gave the finger to America and Europe and headed directly for India. I waited for the M&Ms to take out Goa and Ceylon, then I took out both M&Ms. Wouldn't you know it, but once I had mastered India, my bestest trade buddy Persia declared war on me because we now shared a land border. So I took over all of their lands too. The advantage here is that I could have left the territory of Persia alone, which would have meant that I only had a single land border with a single province, and thus a single foreign nation that I was already at war with. But Persia is pretty rich so I took it anyway. Now I have two full stacks of veteran East India troops in Persia staring angrily across the borders towards the Ottomans and the Russians, just daring them to give me an excuse. With India bottled up, I returned to America and zerged all of North America in a handful of years. Once I finish with South America I'll be back to having only a single territory that shares a border.

OOO! I just thought of an alternative. If you can, give border territories to protectorates who are ALL READY AT WAR with their new neighbors. Protectorates at least tend to remain loyal allies and won't attack you very often, and if they're already at war with their new neighbors, you won't be dragged into any new conflicts.