Battles we see in Edain ranked cup are often won by GG before a good siege has been put into practice unless I'm mistaken.
Each new version of Edain since the initial 4.5 seem to reduce inflation and make the situation of the defender increasingly difficult. And that is what it is supposed to be because otherwise why would we try to get map control at all if a good siege technique was too important ?
Here is my idea to promote siege even more but I must say I don't know if such ideas are technically possible.
The only idea that would in my opinion promote both siege technique and map control would be to introduce a gradation in the final result.
Instead of having 2 possible results : victory or defeat, there would be 4 different possibilites : victory, total victory, defeat and retreat
If that is technically possible, then my idea would be to introduce a new option in the citadel of the starting castle which would read "Organizing the retreat"
By this ability, the player would almost renonce the victory, but after some time after activation of this ability, if he has not been defeated, he will not loose completely the battle and get the final result "retreat" instead of "defeat", and his opponent will not enjoy the final result "total victory" but a simple "victory".
The effect of that ability could be something like that "in a perimeter around the citadel (which would include walls and the battlefield near the castle) units, heroes and building deal 10 % more damage and have 10 % more armor. Outside this perimeter, units, heroes and buildings will deal 75 % less damage and have 75 % less armor" After some time, if the defender is not defeated, the game will end".
With a system like that, the player should understand when victory cannot be achieved anymore and activate the ability not too late in ordrer to organize some defence and stand the ground.
The player who has map control will always win but a good siege technique will also be important if he wants to win the game completely.
In tournaments, the final result could give the player more or less points. In a 1v1, the result "victory" could offer 1 point and the result "total victory" could offer 2 points that could count for the rest of the match.
In the campaign in BFME 1, I remember that there was those 2 final results "victory" or "total victory". This is why I thought that maybe such an idea could be technically possible.
This mechanic would have some interest only with castle start game and not camp start in my opinion