Rendering an enemy territory neutral or blockaded is far too overpowered. I am certain we'll never have a card that does anything like that. The best idea I've seen for a new nuke card is in fact similar to the bomb card but with a slight modification:
- Reduce the armies in a nuked territory to X%
- Reduce the armies in territories bordering the nuked territory by Y% where Y is some fraction of X.
Thus nuking a territory you border can cause you to suffer the effects of the nuke, as you should, and so a bomb card still has its uses. Nukes however can be used when an enemy is stacking behind their borders, as is often the case in diplomacies.
Nuking 1's will of course have no effect. Not sure how you might consider that in "nuke role-play" but it's a crucial weakness of the card that prevents it being too powerful. Pretend you're nuking a desert or something...