Hrm, if the AIP cap for reinforcements is Diff * Diff * 5, that's 245 AIP for a Diff 7 game. I'm pretty sure I was over 300 AIP when I won my first game, so I would have been running into it. I can't imagine getting anywhere near 500 AIP on Diff 10, though. Now that reinforcements over the cap are redirected rather than wasted, is that cap's scaling going to be adjusted? Seems like harder AIs should be fairly aggressive about redirecting strength to their homeworlds and then to offense.
I like being motivated to kill guard posts. It's the one easy decision without huge tactical implications, because it only costs time, and not very much. It's also something you can have inexperienced friends do in multiplayer as a default activity. The only thing I'd worry about was if it became worthwhile to aggressively kill wormhole guard posts, and I can't imagine that being the case.