If rush would be easy like now , everyone could go for it and and make an imba army which results in games with only 1-2 big fights and 10-20 minutes after pt finished games.
Well you can't really remove rushing from a game like that. If the requirement for a sustainable town gets more important, people would still build that town as fast as it is ever possible and then build an army and then have the first big battle and game over. The fastest player will win whatever they are required to do before the only big battle.
If you want to have more battles you would need some kind of mechanism that would favor recovering from losing a battle. For example fast military RE-production + much higher army upkeep rates from the beginning of having an army. So massing a huge army would result in almost certain bankruptcy in case your army is bigger than your town would normally allow to sustain. You wouldve already spent tons of resources to keep that newly massed army alive for 5 minutes. The other player, who didn't mass so big army, could replace his units faster than the rusher can. In this case there could actually be gameplay after the first battle.
I'm not really suggesting any of this but what you would need is a combination of stupidly high and steady upkeep from the moment a unit is trained + really fast unit replacement in case the army is lost. Aka:
1. Reqruits eat 4x less often at inn, so you make as many as you want into the barracks,
2. however the trained soldiers have condition only for 2 minutes and require 2 units of DIFFERENT food for full condition. And you can't order them to eat only 1 unit of food, so you can't send them to fast death after giving them 1 wine.
As I said I aint really suggesting any of this

But that would most likely result in more battles than 1-2.