I thought you were for changing the problem and not debating over whether it was a good idea or not.
I'm all for both, but I didn't see any reason to discuss whether it was a problem or not when we didn't have any alternatives to compare the problem to.
What if the enemy is attacking? Should he be able to gain more of my zones by taking advantage of the revolution mechanic?
Your revolution mechanic still assumes that you don't fully conquer the enemy. You should fully conquer the enemy or find more allies so the revolution mechanic can be used once the way it's meant to be. If you overpower all other players enough and outsmart them strategically, you'll still be fine.
You can pick either depending on what you think is least of a problem to your nation, but I don't think revolutions are overpowered. The one who revolts would hardly win the game if there isn't a revolutionary change in the rest of the game. The one who is revolted against loses 10-20% of its zones from its border rounded down, in your case that'd be 5-11 which is hardly more than the small nations have currently. I do think revolutions could be improved, maybe with having to start in previously owned territory if you're eliminated, or with a time limit on (like must wait 5 turns since conquest and max 10 turns), or something else which would make people actually eliminate other nations again.
But again, I don't think revolutions are that overpowered, if they are at all. They might tip a war, but then you need to become stronger, just like if it were the pure production which tipped the war, or the trade between nations compared to you being alone which tipped the war.
Don't attack enemy zones and then give zones to an ally in a way that you are able to move forward and not be able to be attacked without allowing you to cause a revolution.
I think this exception is too specific. Maybe something like "you cannot transfer zones which one of your attacks depended on the same turn" or something like that. Because that also does look a bit stupid on the map indeed.