Remove technologies and research. I don't like technologies because technology tree doesn't change from game to game. It becomes boring very fast to select techs from the same tree. It kills replayability. Some randomness in tech tree can partially solve the problem, but it is for developers.
Remove improvements except for wild improvements. So shards, metal, crystal, logging camp, etc remain. The reason is the same as in technologies. Ordinary improvements are the same in every city. It is boring to build the same improvements in every city. It kills replayability.
Allow access to weapons/armor/items depending on city level. Level 1 city allows to use Common weapons/armor/items for trained units. Level 2 city - Uncommon items. Level 3 city - Rare items. All high-end items would be Rare. This idea solves problem with city spam and game slowness.
Add +1 counterattack to all monsters and melee weapons. Add unlimited counterattack to daggers and swords. I don't like units without counterattack because they are like cannon fodder. Also this idea solves problem with weapon disbalance.
Add gildar cost to trained units depending on production cost. This idea makes gildar useful and prevents unit spam.
Each member of 4-troops would cost more production and gildar than member of 3-troops. The same with 5-troops and 7-troops. This idea solves problem with obsolescence of small troops.
Stats in uncommon and rare items would cost more resources then corresponding stats in common items. For example, Common sword has 10 attack and costs 1 metal. Uncommon sword has 20 attack and costs 2.5 metal. Rare sword has 30 attack and costs 5 metal. This idea solves problem with obsolescence of weapons/armor/items.
Set army size to maximum from start. This idea adds a choice: to use either many weak troops or a few strong troops.