Need a theme for a solitaire worker placement game

I am currently playing "Lords of Waterdeep" a lot on my tablet and I have some interest in making a solitaire worker placement game. I have some ideas for the mechanics, but have little ideas for the theme.

I am not a huge fan of worker placement game, but I have a few set of mechanics I intend to use which comes from the few games that I liked.

Originally, I wanted to use ideas from "Leonardo da Vinci". You would play some sort of mad scientist trying to fulfill inventions and sending minions to acquire resources (Think Dr Wily in Mega Man). I would have use the invention construction and resource gathering mechanics of "Leo.da Vinci".

For the player's opposition, I was thinking of something like Ancient Worlds where in my case AI put "workers" in worker spot or area containing various worker spot to increase the security of the location making it harder to use (there could be 3 areas where buildings get placed). The AI would add "security" with time making early worker easier to place than late workers. Players could have workers of various strength and specialty.

In "Lord of waterdeep|, the intrigue card system could instead be used as a list of events and opportunities that remains for a certain time that the player can try to comple. I could also have cards in hand used exactly like "L.of W." intrigue cards. I'll see if I could use both.

Another thing I like about "L. of W." and "Caylus| is the building system: Make a building that other players can use. In a solo game, such thing cannot be possible since there is only 1 player. But I found certain alternative mechanics with similar gameplay. I tought it could be used in a "Just Cause" or Rebellion theme game where the player can put Agents on the government buildings. There is various kind of outcome possible:

1. When the player use a building the AI gains a reward (similar to the original mechanic)
2. When the player does not use a building, the AI gains a reward ( the player did not steal the resource, so the AI get's it)
3. As long as the building is standing, the AI gains a reward (players can keep building in play for it's ability or destroy it to prevent AI to get resources)

Option 2 seems like the best so far as destroying buildings in a worker placement game is not really a good thing especially if your nb of worker increase with time. If new buildings get added through the game, then maybe I could use method 2 and 3 for more depth. The player will have to judge when to destroy or not a building.

Any suggestion of theme for such mechanism?