Glad to hear that GalCiv2 is going to get some loving care!
Elestan's posts at https://forums.galciv2.com/394055/page/1 have many suggestions which I think are good.
Some additional things I'd like to suggest:
1) Improvement. Most (all?) scroll bars in the game are hard to use on a high res screen because they don't "capture" the mouse the way Windows scroll bars do. If I move the mouse off the scroll bar while trying to scroll up or down, the scroll bar loses capture of the left button which I'm still holding down.
2) Bug. When I click on a scroll bar in an attempt to page up or down, sometimes instead of moving by just one page the displayed items move to the clicked location on the scroll bar.
3) Bug. My ships occasionally don't display in the main window. The tile they occupy is just blank. I've discovered such ships by using the tab key, they display once they become selected.
4) Bug. Sometimes it is not possible to purchase an improvement in a planet's "build queue". The "buy" button is greyed out even though no improvement has been rushed on the planet in the current turn and funds are available. Usually using the "X" key followed by "Z" to redisplay the planet screen fixes the problem, the "buy" button is then enabled.
5) Bug. Setting a planet's launch direction often doesn't work unless one is zoomed-in to a fairly high degree. This is on Elestan's list as number 44) but I want to add a bit of information which might be useful. After selecting a planet and hitting "L", I can move the mouse so that the direction I want is visibly highlighted, then left click and not get the desired result. It seems that the logic which decides which direction to highlight based on the current mouse location is not the same as the logic which decides which launch direction should be selected when the mouse is clicked.
6) Improvement. Please don't show the message box for "survey xxx cannot detect any new anomalies" when the game option "show found anomaly popup" is turned off. This message box can cause an annoying inter-turn pause which isn't useful when one has become uninterested in the details about automated survey ships.
7) Bug. When I double click a military starbase for which I have set "allow auto build by priority" and I've reordered the "module priorities", I often see the default ordering of priorities, not the priorities I previously set for the starbase. This display should always show the priories which were previously set by the user for the starbase.
8 Improvement. After deleting an improvement in a planet's "build queue", I'd like the next item in the queue to be auto-selected. This would make it easier to clean up automatically scheduled improvements which aren't wanted, e.g. after taking a planet from an AI.
9) When I take an AI's planet I sometimes see silly misuse of bonus tiles. A common example is farming - often the AI has built something else (e.g. an influence improvement) on a tile with a farming bonus, yet has a farm on some other non-bonus tile.
10) Occasionally auto-routing of a ship foolishly takes the ship through an asteroid field, killing its movement.
11) The AI is very weak in replacing ineffective improvements. E.g. if I gift an AI a planet with no starport, many fertility bonuses, no farms, and all tiles improved (say with xeno labs), it won't "upgrade" the xeno labs to something more useful such as farming. It seems to lock in to the idea that existing improvements should only be upgraded, not replaced.
12) Run in the background. The inter-turn delay after I hit the "turn" button takes a long time when I'm playing a game with many planets and ships. When I use alt-tab to do something else in the meantime the game stops. I understand some reasons for this (don't hog the cpu and memory) but these factors don't apply on my computer. My laptop has 4 cpus and more memory than GalCiv2 can use. Please add an option flag which allows GalCiv2 to continue running while I've switched to another window. That would allow me to run it on my main/fastest computer instead of my current mode where I run the game on an older auxilliary computer which I dedicate to GalCiv2 because as it stands it pretty much needs its own machine. (I could run a VM for GalCiv2 but I'm not willing to do that and I think most users wouldn't even know of the possibility, much less the trade-offs involved.)
13) Deleting rally points. I can't seem to get rid of a rally point. I can remove one but when I next load a saved game to continue, the deleted rally points still exist in selection lists though they are not visible on the galaxy display.
14) Slow response times. When a player has hundreds of ships with predetermined directions and/or hundreds of planets various aspects of the game become rather slow. The inter-turn time with many ships moving is especially bad. For those crazy players going for high scores, thousands of ships in transit result in inter-turn time which are crazy. I know there's a lot going on (route calculation, military strengh recalcs due to location, fleet selection for auto-grouping, checking for guard activity, etc) but nonetheless I'd be surprised if an improvement of at least an order of magnitude isn't possible without much work. A dramatic speed up would make a big difference to many dedicated fans of the game.