I'd like to see either an improvement to borders placement logic, or to have the game describe it in greater detail.
Currently, it seems like it chooses an arbitrary ordering and focuses defenses there. This often leads to having an island in the middle of nowhere being turned into an 8, and main regions being completely undefended. It'd be nice to have something more consistent, and closer to what a reasonable person might do. You obviously already have to calculate the size of clusters for reinforcements. You could weight the likelihood of reinforcing your largest valued clump higher. Perhaps build up to parity first on the main clump, with preference towards defending against larger values, then going for 1 more on the borders, or parity on the other clump borders. A bit of randomness would be nice, too. It seems like currently when it puts troops where you don't really want them, it will stick to that for the entire game, regardless of how in trouble other borders get.
I feel like those changes would take a lot of the luck out of borders. If people knew roughly what behavior to expect, they'd be able to take advantage of it, leading to a greater reward for good positioning, which is what borders is all about.