I'm playing through a similar scenario at the moment, however the 5 other nations are all being run as NPRs, as a result I have absolutely no information about the status of the other powers relationships with each other. I have no idea of the population, production, research strengths and weaknesses or fleet strengths, no idea even how far they have explored, but I see a chinese gate builder wandering around sometimes.
In one way it's disappointing as I lose out on all the political and diplomatic interaction that I've grown accustomed to, but on the other hand it's good because I'm virtually in the dark about my potential adversaries. Except for all the intelligence I have gathered about the swarm of ships rushing through the solar system, the knowledge is very rudimentary and I don't even see most of them on sensors most of the time, greater investment on sensors will help with that, but I do appear to be outnumbered and the truce timer runs out in 5 years.
I'm wondering if a future version could allow more information to be gathered on NPRs as a result of spies, or even minor intelligence just from having good relations and trading. Specifically economic information, knowledge of research they have (not stealing the tech itself) and maybe information on exploration, colony location etc, and some indication of how NPRs are interacting with each other.