When I first played Age of Wonders
I didn't think much of the townsieges. I don't know how it was in Master of Magic but in AoW it was very simplistic. Defender moves first and moves his archers to the walls (there's no towers or heightdifferences) and starts shooting. As the attacker you move your archers to the walls as well and got 50% chance for the arrows to go through the wall and have a CHANCE to hit the units defending.
Age of Wonders townbattle with wooden wall
Age of Wonders townbattle with stonewall
Age of Wonders II and Age of Wonders II Shadow Magic however
introduced the best townbattles I've seen this far in a game with individual units. Now the defenders were positioned higher than the attackers and thus archers had better chances to hit.
The height difference also forced attackers who attacked through the gate (which is weaker than the walls) to go 1 by 1 so the defender could use two melee units to almost block the gate with.
This did enable the attackers to attack first (and with charge they could inflict good damage) but that's the price you pay to be able to attack with two units. An attacker COULD walk away though (both to the sides and back but then he would get hit by all your units that are in meleerange.
I’d also advocate a “laying siege” mechanic where an army surrounds a settlement without actually going in for the kill. Armies should not be able to move to a city and attack the inhabitants in the same turn unless they have the means to do so (ie catapults). The attacking army should have to wait a number of turns before attacking, based on their amount of siege equipment and the quality of the defences (ie, walls). Right now it is too easy to sneak attack cities in one turn, and the increase in basic movement will only make this worse. Imposing a turn delay would give the controlling faction time to come to the town’s defence. Otherwise you get a situation where no one ever attacks a city unless they know they will win, making the battles non-events.
I believe you base that opinion of War of Magic alone. In Age of Wonders, you HAD to have a unit with 'wallcrushing', 'wallclimbing' or 'flying' to be able to assault a walled city but that handicapped the A.I since you could send out striketeams to destroy them and then the A.I had to rebuild and send them at your cities (again).
In Age of Wonders II, any unit could capture a city (which was LOTS better I tell ya!) and that improved the flow and speed of the game. Only two units could hit a section of the gate or wall (though only wallcrushing units could hit the wall and they also did double damage to the gate and wall) and without wallcrushing it took ATLEAST two turns (mostly three) for two tier 3 units to bash down a wooden wall (which had 20hp) and around five turns to bash down a stonewall (and with ranged defenders that's suicide).
So from an Age of Wonders II perspective what you suggest sounds insane. And who knows how much Derek will change the sieges?