That rule would almost be impossible. Effectively the whole game wouuld rely on DTF to get any other points. The opponent would just have to drop a 3xlanda or 3xThunderhawk to prevent them from getting any points (TSNP being a bi-product of them gaining any points). It is just not Epic, and I would not play such a list with a restriction unless all troops were significantly discounted.
I like the GT game and the force is made to be able to play in any scenario - rather than force a special rule into a scenario.
All defense and no attack makes Frogbear a very grumpy boy.

yeah that's why I said "something like." It's just a brainstorm and needs work to make it more fair etc.