That's a bit of shifting the goalposts here. If we're now talking about cities that already grew a bit, then it's not reasonable why we shouldn't already have a construction yard there. That building isn't THAT expensive hammer-wise.
Not really, you can get a city to 5 population really fast if you kill the animals around the region you built it. If you do this, your city will reach a considerable size in a few turns with nothing built on it. I personally do this all the time i found a city. Already reported i think this mechanic OP, but, unfortunately it requires dll modding.
About the construction yard, you will need to invest a few turns there to get its benefits (it will take at least 15 turns in marathon, and since i only play on this speed, all my feedbacks are based on it). Grow the city fast by killing animals around and put 2 engineers there and you will receive a + 8 production bonus. Nothing bad for something that costs 150 hammers on this speed. This civic is great for those "on demand" things.
But, if the community feels that liberty is underpowered, why don't add something nice and unique to the civic, instead of exchanging it's uniqueness for something boring, like 100% gold, research, etc... ?
The civic does a great job simulating the meaning of freedom (you can be whatever you want), but, if its weak, why don't make the civic simulates religion freedom as well ? Like, allowing the player who adopts the civic to receive the benefits of other temples, despite of having their religion as official ?
So, if you want to get more health, you can choose to get fellowship of leaves when discover a second religion, or if you want more xp, you can choose the order (if it goes live the way its on the future changelog), and so on. Maybe halve the beneficits of non official religion temples if its too powerful ? Keep in mind that you can easily discover 2 religions if you have the priests' guild.
This would add something unique to the civic, since it would be the only thing in the game making the player pursue a truly multicultural civilization.
Also, if the unlimited specialist is perceived by the community as a weak feature, due to all specialists slot you can get (again, you will have few merchants slots if you don't have mechants guild, so this is not true at all), i think it's better to reduce the specialists slots in some buildings, than removing the uniqueness of the civic. So, the construction yard would give only 1 engineer slot, instead of 2, for example.
I agree that, from a realistic point of view, makes no sense the increased maintenance, but, i can easily overcome this by thinking this is to simulate the choices people do. Like opting for not working, or to become an artist instead of a merchant, or an artisan.
I also want to point out that my feedback is based on my last playtrough, with the Elohim/ Empyrean combo.
And finally, i am not a modder, so i don't know if my suggestion above is viable. All i know to do is brainstorming