Progress update 2019-09-10:
The current phase of the Create New Game window is done! New build is pushed. The 'new' button on Game Details is re-enabled, and most of the Non-AI controls on the Create New Game window are now functional. Previously, the Create Game button would essentially import a static dump of a game I had generated on the A4X side. It now generates the game from scratch, based on the parameters selected.
The following controls are now functional:
Starting Year
Max Number of Systems
Local System Gen. Chance
Local System Gen. Spread
Construction Cycle Time
Min. Comets per system
Empire Title and short name, Species Name, Homeworld Name
Government Type
Main Empire Theme
Commander Theme
Technology
Max Deviation in Oxygen pressure, Gravity, and temperature
Max Atmos Pressure
Starting Population count
Wealth Creation Rate
Industrial Percentage
Number of starting Shipyards
Number of starting Research Facilities
No missile bases for conventional start
number of Sol Jump points
System Body survey completed
Jump Point survey completed
Starting Tech points
Generate Sol System or SM game
Jump gates on all jump points
Realistic commander promotions
Commander political bonuses
Real Star systems
Orbital motion for planets/moons/asteroids
These all have fully functional impact on gameplay. For example, the Government Type setting and starting population have complicated and widespread effects on what you start with on Turn 1, especially in a Trans-Newtonian start.
Game name and SM Password were already done. The remaining controls record their settings in the proper place in the DB, they just don't do anything because they are AI related. I've updated the mouseover tooltips over these controls to say that the settings have no effect in-game.
I've made just a couple tweaks to the UI to try and reduce some of the ambiguities. Controls that have no effect under certain conditions, such as Local System Gen settings in a Real Stars game, will become disabled and say N/A when they have no effect. 'Number of computer controlled Empires at game start' is another control that will go N/A when the box above it is disabled, and I updated the wording in the section.
So now system generation and new game generation are done! Those were the two areas I was most doubtful of whether they would be possible when I started on Q4X! I'm now going to move on to a multiple-race game. Q4X already fully supports multiple races but I need to add all of the features that have to do with races interacting with each other. (Minus combat, that's for later). I also have to do some general testing to make sure switching between races is a smooth and bug free process. After multi-race is done, my focus will be on finishing all the gameplay features that do not have to do with AI or Combat, so that empire growth and exploration is fully playable. That will of course be over a series of updates; there are a lot of core mechanics still missing.