The original game's combat design feels weak. The requirement build military buildings to be able to expand borders to build civilian buildings results in tons of wasted knight huts. The restriction on building military buildings too close to each other is a hack to limit an obvious exploit (building tons of huts to better defend territory) when it should instead be wasteful to build too many military buildings right next to each other.

Ideas for overhaul:

• allow attacking knights to burn enemy buildings directly, and possibly chase down and kill serfs (though that would be cumbersome because of the one-serf-per-mappos limit). Attackers would no longer be required to attack enemy military buildings only.
• possibly, instead of directly targeting buildings, allow knights to be sent to attack any enemy flag, with a game option to pillage/no-pillage and any enemy civilian buildings encountered along the way will be burned.
• enemies entering friendly territory would automatically trigger garrisoned knights nearby to sally out and intercept the attackers, engaging in field combat. A new menu/mechanism would allow configuration of sally/no-sally and the ratio of knights to send out
• no more "100 morale" for defenders, instead defenders use their existing morale, with a boost for being in friendly territory, an additional boost for being near a friendly military building, with increasing boosts for stronger military building types (tower, fortress/garrison, castle). Further, an even larger boost for actually being inside the building and defending it "the usual way" instead of sallying

Longer term ideas:

• Perhaps eventually, the ability for knights to "camp" in enemy territory, or anywhere else, by allowing knights to construct a tent that acts like a knight hut for the purposes of being able to stay put and be sent back out to a new attack target so knights are able to attack things farther away from friendly military buildings. The tent would offer no defensive bonus. It would need a flag and would need to be attackable which might be complicated to code, resulting in enemy flags inside player territory.
• Allow friendly knights to rally to a specific area for defense, and stay there until called back. Similar to camping above but in friendly territory. Possibly same mechanism
• Allow building outside of "player borders", the player borders would instead only represent area that is protected by friendly military buildings in terms of the range of triggering auto-attacking against intruders.

These changes would make it mostly pointless to build military buildings very close to each other and that limitation could be removed.