I don't know much about how the game is coded. But a game like this still having display bugs really irks me.
1: Fix the displayed values, if a bonus is listed as a %, then it better be a %. Many bonuses, like sensor range, engine speed and trade routes should be displayed as an absolute bonus, but are not. This fix should apply to the tech tree notes, building bonuses, planet details tab and race summary tabs.
2: Hardcoded different rules for AI and human players (regardless of difficulty) : https://forums.galciv2.com/361996
"Automated survey human flagships are not affected by fog of war."
3: Fix the summary tab - currently it does not display bonuses from random events, morale events, moons and such making it pretty useless for evaluating your production and research. You have to go to the planet details screen in order to view them.
4: Keep the ethical random events (from colonising a planet), even after choosing an alignment (researching Xeno Ethics)
5: Reduce micromanagment by fixing the rush buy costs (it should never be cheaper, overall to pay in installments)
(Currently is is cheaper to use Terran Manufacturing if remaining production is 28 units or less)
6: Don't make colonies pay for wasted resources (assuming this is still true)
"Excess military production (production over price of the ship - e.g. ship costs 40MP, planet produces 200MPs, so excess is 160MP) is lost, but player still PAYS for it."
7:Fog of war not reforming
8: release a summary of how tech depreciation actually works, there have been many threads guessing this - but there is no consensus.