I disagree that resource management requires no skill, but it is true that fixating control in guild will lead to imbalances and frankly, it removes some of the thrill in the game, especially if guild becomes the only way to get control.
About making TP and DD accessible for all schools of magic like magic arrow, I don't think it is a good idea. Right now, I think the balance between might and mage heroes is quite good, might heroes are necessary for main hero purposes, and good mages are also needed for control wars, and in many cases mages make good main heroes. Making TP and DD to every magic school would make might heroes stronger again, since it does not matter which schools of magic you have.
The problem of 2 players getting control 7-10 days apart exists of course, the way we approach this is the question. I could imagine trying out increasing movement cost of TP and DD, this would increase usefulness of fly, because right now it is really inferior compared to the other 2. Also it would not create so many imbalances where one player just takes all enemy towns in a couple turns and it is game over. This would make games longer of course, but it is a trade-off to be considered.
I would prefer that we keep the game close to it's roots by not changing it too much. So I would not take a radical approach like completely removing control outside guild, or fixating control spells in 1-2-3-4-5th build, it takes away from the diversity of the game.