Just three wild ideas dropped on my head while I was drooling thinking about how the game would eventually be like.
Terraforming: I've been playing a lot of Surviving Mars, that game focuses heavily on terraforming mars. Although rationally I agree with the mainstream view that terraforming Mars would not be as easy or as necessary as our modern day Sci-fi depicts. But gameplay-wise, I can hardly think of a better end game goal for colony management gameplay. I'm saying this because it's already pretty obvious that colony management would very likely become a vital part of KSP2 gameplay.
If I chose to be a colony-minded player, after a hundred hours into the game, all the resources and technologies I pooled together on Duna would surely be rather sizeable. Eventually I'll need a rewarding sink hole to dump them into, terraforming would fit in just right as such a sinkhole.
Dynamic career science: Now this is a heavy one, it's in some ways a revamp of the contract and milestone system.
I can't honestly say that I'm satisfied with the "point buy" system the current science tree relies on, it's grindy, static, immersion breaking, and makes very little sense.
I wish to see science point become more subtle. The player, instead of purchasing nodes in the tech tree with "blue points" earned by biting extraterrestrial dust, complete certain milestones to stimulate the development of the scientific progress in that particular area.
For example, the "Basic Construction" tech has a progress bar which grows by 1 point each day, representing the day to day science development. It will unlock itself after some time, along with some other techs of the same tier even if you do absolutely nothing other than time warping forward. However, if you complete the mysterious goo and material bay related milestone, the achievement would give its progress bar a plain point boost as well as applying a modifier to the natural growth of the material related techs, for a certain period of time.
I believe this is somewhat closer to how space programs impact our science progress in real history. And instead of grinding for contracts and repeating experiments, the player should be rewarded for planning their space programs strategically.
The anomaly hunting would fit in well with this system, the player should receive some very unique boost should they detect and properly study an anomaly.
This should also synergize well with the colony system, because a colony is inherently, time sensitive. Time becomes a vital resource with this system, a successful colony, be it a scientific outpost or a giant habitat, provides sustained boost to science progress, but it also requires maintenance and supply from time to time. This system should encourage the player to design and plan their colonies strategically so as to achieve net positive output with their investments.
Cinematic Camera: This one is somewhat trivial in comparison with the overhauls above, but with KSP2 aspiring to be such a beautiful game about such a beautiful universe, it would be weird if the player is not granted the proper tools to capture such beauty. I wish to see more sophisticated camera tools implemented into the game, with lenses, apertures, focal lengths, even camera rails, tail-followings, etc. I can already see players taking pride in their own creations, why not let them film their own documentaries?
I guess that's all for my daydreaming, I'm looking forward to seeing other players expanding upon these ideas in this thread.
And thank you, team Squad, for such a fabulous game.