Here’s a fairly simple solitaire variant for Carson City which plays pretty well. You’re playing against the game to attain the highest score you can, and there’s a “dummy” player trying to impede your development of Carson City as much as possible.
Basic rules remain unchanged, with the following additions and changes:
First of all, the “dummy” player places a cowboy (these will be referred to as “dumboys” from this point forward) immediately after you place one of your cowboys. Dumboys are placed as follows: 1) on the “action track,” roll a D6, with your cowboy considered to be on (or as close as possible to -- adjust as needed if the 6-square sequence would go over one end of the action track or the other) the #3 square, and place the dumboy there; 2) in the land area, use this same basic process, but expand it into a 6x6 grid -- start left-to-right, then top-to-bottom, adjusting as needed if the grid goes over an outside boundary and considering your cowboy to be on (or as close as possible to) the #3/#3 square; 3) if the dumboy lands on an already claimed parcel with no cowboy or building, move him to an adjacent square with one of your cowboys, if there is one -- if not, to the highest producing adjacent building, if there is one -- if not, to the adjacent unclaimed parcel nearest to the center of town. Thus the dumboys will be looking to duel one of your cowboys, to steal half the income from one of your buildings, or to claim an unclaimed parcel, in that order of priority.
You can challenge a placed dumboy to a duel if you want the square he’s on. And if a dumboy would be placed on a square already occupied by another dumboy, just discard him. All dumboys are removed at the end of the turn.
Which then brings us to duels. For the dumboys, during the first 2 turns roll a D6 and count the full value -- then roll again, and add half the value of that roll (rounded up). During the final 2 turns, add the full value of both D6 rolls.
Lastly, personalities can be used for only one turn -- then choose another from those left. Note that you can increase the difficulty level by shrinking the land grid used for dumboy placement (e.g., 5x5, or 4x4...) and thus increasing chances of duels -- but remember that you will have quite a few duels on the action track, where there’s a 1/6 chance of a duel happening (actually it’s higher, as any 6-square sequence can overlap other cowboys already placed).
So give it a try, and see what you think. Any feedback, suggestions, and further “tweaks” would be greatly appreciated!