Yeah if I could keep the actual sieges on the campaign map but then have the city battle replaced by a field battle, I would. I just don't think it's possible to mod it like that.

That is, you would have to put a lot of garrison in each settlement, because if you don't have an army nearby...

The way I had to implement this is that no more sieging is required on the campaign map. All cities are basically minor settlements now when it comes to walls. It's not ideal but it's the only way I could find to achieve this.
Do you mean mods like mk1212? If so this mod might work with it depending on how they implemented their changes.

I've been waiting for this mod for a long time, thanks! Do you think it would work with the mods that wall off all the cities? I mean, there would be turns to besiege it, but it would be an urban battle, right?