I too, like this idea. We should call it the projection of off-world power update, or POOP for short.
There are so many ways this could be calculated but the biggest hurdle seems like it would be the AI routine for the diplomacy score alteration avoidance. Basically, how and when an alien power would decide to ignore an established border and it's decisions on how to proceed if it was covertly breaking that border and was discovered.
Is there a features thread for version 6.x+ or is it just the bug thread? The original 5.7 requested features thread is stupendously long so I would be loathe to place such an excellent bud of an idea in that thread only to be quickly lost in the horde of previous posts.