So the reason I am making this suggestion is because I think that Nations as a game mode is full of issues that simply can not be fixed without taking away the game mode from people who have grown to like it over the years.
But as everyone knows, Many things were suggested in the past that may have been good ideas but were simply never explored because the change is too "radical" to be implemented in Nations.
And for such Radical ideas (given that they are not a waste of time to code/implement/make somehow) There should be another game mode, that can be aimed towards resembling vanilla Factions much less than Nations does and therefore being much less restricted in terms of ability to make change.
The game mode can be semi-permanent, meaning that it can just be themed as a big "event", maybe some kind of large map with pre-determined conflict that needs to play out between two or more sides
For example, it could be World War I or World War II re-enactment with pre-made factions, sides, and significant towns (or some imaginary made-up conflict if world wars would be too "controversial")
There could be a week-long "grace period" before the war starts, and then as time passes new "Technology" gets unlocked, like unlocking Movecraft classes, or weapons with the passage of time.
Guns could be much more powerful but checked into balance with bulletproof vests (that significantly reduce damage from guns but make you very weak to swords since you don't wear a chest plate)
Claiming can be done without any "power" limit, only limited by the amount of gold each side has. And the sieges and territory gains and losses can be done with a special war mechanic that allows for realistic territory dynamics (if i explain it here it will take a massive wall of text,i just want to see if anyone would be up for something like this first)
Victory could be achieved by one side taking most or all of the settlements of the other side, and after that the game mode is simply removed, possibly re-started some time in the future and stats like top 10 people by balance/kills/points gained can be saved on some special wiki page about that event.
SO naturally, in such game mode, it would not matter as much if certain mechanics are straight out broken, or if some weapons are impossible to balance because at the end of the day its only temporary and more aimed as fun event and not a sweaty competition that Nations has turned itself into.
If some mechanics that were used in the game mode turned out to be "beneficial" or could be seen as possibly able to solve exiting problems on Nations, vote could be done to determine to implement some of those to Nations.
The event should last anywhere between a few weeks to a few months and could be done just once, or maybe repeated many times depending on how it all went.