Worrying about invasion and warfare isn't the best way to go about choosing a plot as that's really not the culture of the "game" or community anymore (for the better I think). There are elements of warfare of course, though I think there's a greater emphasis on detailed tension or intrigue leading up to a war.
I'd highly recommend that you choose an arrangement that borders or is nearby active nations. Staying in the proximity of activity is by no means a requirement or anything, I play a nation of islands in the corner of the world with fish for neighbors - but that takes a great deal of patience and confidence (which is a struggle) in the internal/domestic RP product that can persist without daily or weekly interaction with neighbors.
I'm more worried about knowing where I am geographically, so that I can come up with a prior history based upon it. It's also a matter that I'm starting fresh, and thereby trying not to tread on any toes immediately.
It's not all about war, but I did think of it as an idea to prompt reactions after reading Oikawa's blog post about activity in Europe. Broadly, however, wars are not the idea: just an immediate, polarising catalyst to prompt international responses, like the Suez Crisis.
I do also think that interaction goes far beyond border-related issues, especially when one is still in the immediate vicinity and geographically 'European' or its equivalent.