Love the game, very addictive, it does mostly capture the essence of a civ game.
I would love to suggest a few tweaks, especially around resource gathering.
Firstly there seems to be no weighting on resource collection, so you could have been waiting for several turns for a resource, only to have the AI swoop past and "steal it", I feel this would be more balanced if it weighted the randomness towards "time spent in square / adjacent square".
I also I feel players should not be able to build towns when adjacent to another conscious player, currently again you could be waiting for several turns to build a town in a square only for the AI to swoop in and builds a town next to you. Combat here is very lack lustre, as if you both have swords, what should be a draw, actually results in the AI winning as it can still build a town as they are not impediment-ed by the draw. If they were forced to knock you unconscious it would give them motive to attack you, and make it a fairer fight. An alternative would be to ban both sides from building a town after a drawn fight, to make either side move off or pursue etc.
Lastly I feel towns / cities should attack opposite players in a similar fashion to monsters, forcing the AI when it's camping your resources (which again seems to have a favoured weighting against a town) to defend using swords, or be knocked unconscious.
Weighting resource collection by how long you've stood there: Very interesting! I hadn't thought of that. How would it weight buildings, which stand there the whole time? That logic for collection probability is already fairly complicated, but I'm interested in thinking about this suggestion more.
I agree that combat is lacklustre! I'm planning on reworking it (yet again!) but don't have a concrete plan yet. Your ideas here are interesting, but I've been very careful to try to keep everything as streamlined as I can and avoid introducing special cases, so I'll be hesitant to make building rules more complicated. I might prefer simplifications like always giving resources to buildings instead of heroes, or something like that.
Towns/cities attacking: Cool idea - I'll think about this, too.
Thanks so much for your feedback and suggestions! This is definitely what I need. If nothing else, then for motivation to keep making improvements. :)