Wow! There is so much polish on this, the UI looks absolutely fantastic and I'd love to know a little more about what's going on under the hood as I can see you've said it's a custom solution.
I'm really glad that those many hundreds of hours in KSP have paid dividends here. I suspect it might not be too intuitive for those that haven't played similar games in the past, so mileage may vary. But I certainly enjoyed thinking about things manually and not relying on mechjeb.
I'm not too sure if I have anything too constructive to say here, I exclusively ended up picked the scan speed upgrades as fuel and the trajectory trace never felt like something that was ever lacking.
Great game, thanks very much.