I don't like using gold to make improvements, esp if the benefits of many of the improvements are that they earn you extra gold. To me it would have to be a really clever and novel system to want something other than builder/worker. Not gold, not city build queue like everything else
I did not say only and certainly not city queue. But lets be nuanced.
Civ has actually only two major resources when building, gold and production (queue). And they are not independent of each other cause you can buy production with gold. And production and gold can be used to increase production and gold output in the city in the long term. So for starters saying it has no sense to use gold to earn extra gold with improvements has no sense. All game systems in Civ VI work like this already.
Regardless lets take a look to the improvement system, shall we?. In Civ I to V builders use "production time - gold" to produce, and improvements require turns so when you improve something u cannot have it instantly. The cost is "production + gold + game time".
In Civ VI, the cost of improvements is "production + gold + player time". Here is how it works: Civ VI designers said: We don't want players to wait for improvements. So lets make them immediate. But then they thought: well that may be too easy cause they would be able to build too fast. So decided to made improvements instant, and at the same time they made them take longer as builders get spent, and take time and resources to rebuild and to move again and is a never ending cycle of wasting the player time doing repetitive actions, instead of making the player wait one turn, while playing doing other things... I say it again: the aproach of Civ VI is to waste the time of the player to keep the player busy instead of making the player wait while playing.Civ VI just replaced interesting gameplay for repetitive tedius time wasting activities. This seem to be a core philosophy of the system. To give the impression of instant build gratification obtained by wasting your time with routiune click actions. It is a mobile game mechanic.
I said building improvements should cost money, cause pretty much that is how it actually works. Public works cost money. That is not saying the game should work as it does now. Cause the economy should need to be reworked...
Do we know a game that had a economy system with taxes that could be increased or decreased to accomodate for building more stuff at the cost of happiness (for example). And where u know, there is an actual point in economy. Cause that would be the system I propose...
And also, that game was Civilization I. Let that a testament on how much the ball was dropped here, and how bad are some of the ideas in VI.