https://forums.frontier.co.uk/showthread.php/383217-Frontier-Expo-2017-Recap <- Full stream link in the OP
2018 is Core revamp:
Trade, Mining, exploration, alliance ships, engineering, planetary tech, galnet audio and a bunch of other things.
Also unknown premium content
Go back 6 months and exploration + core mechanics were the number one most wanted thing. As mentioned above the very second this was announced by FDev people were disappointed that Atmo landings and space legs were not on the menu. Don't expect space legs or atmo planets in 2018. I suspect maybe volcanic planets or gas giants may become landable/flyable in the premium content though. After 2018 who knows
Hopefully this gives you an idea of whats on the way.
For game engine limitations check out Jurrasic World or Planet Coaster, I don't think it's a limitation as such but it's as you say, no easy feat.
I agree sometimes the community can make really good input and I have been one of the ones calling for more community interaction earlier in the dev/design process. I don't think it should be a floodgate though with anyone and everyone. Make it a special club where FDev can pick and choose critics and contributors who are trusted so they get good solid feedback without spoiling secrets to come.
They've done this before with certain livestreamers and stuff so it's possible.
Others will very strongly disagree with my "club" idea and have valid arguments. I just feel personally thats the best way to get it done as even the beta is like being caught in a tidal wave of feedback threads these days.