Once the game advances to its next iteration I think I would dearly miss the dual-build queues. I loved how you had to wrestle whether to build a starport on a planet or dedicate it to research, culture, or wealth, and then even if you built a starport you could decide to focus on social, military, or research whilst balancing resources depending on the micro/meso/macro environment at the time. I personally would love to see the separate off-planet starport as the (advanced) starship queue, I can vaguely recall something ingame alluding to this already (can't remember which tech off the top of my head). The next question would be whether an advanced off-planet starport would be vulnerable to attack/raids in which case would it need to become part of starbases (and have in-built defenses etc).
I am with you with most of what you said here. I think I would grow to miss the dual queue in GalCiv 3 as the state of the game advances. If only because the way I play GalCiv 2 makes use of it.
At this point I am interested in how a separate ShipYard would be implemented. There are many nice possibilities to it but some potential caveats.
One thing I would like to point out is that I do not see how this could be implemented in the current Production wheel without adding a new slider. For some reason I have the feeling that StarDock wants to try to avoid adding more sliders to that screen. The problem is that as much as the production wheel is great, fun and easy to use, the design is hard limited to 3 options.
To add a fourth parameter You would then need something like that: ( Imagine a slider just bellow the wheel that gives the percentage of production that is sent to spaceport instead of social production.)
I made a demo by Pasting the slider from GalCiv II in using MS paint
Furthermore, a Separate Shipyard that you see on the map could presumably be attacked and destroyed. That could expand the strategic depth of the game but also open the door to some Checkmate style of victory. Which might be a bit cheesy when pulled off.
Imagine a player gets rushed and have his starport destroyed and has no military ship currently out. That is basically Checkmate GG. Unless some of the more basic type of ships could also be built on planets, Say Tiny, small and cargo Hull can be built on both planet and Spaceyard, but bigger hulls only in Space.
I am really curious about how the separate StarPort could be implemented. Please share your ideas on the subject and of course if StarDock pitches in too that could be great