To my dismay, it seems that not only is the Manhattan Project a Great Wonder that enables nuke-building capabilities for all civs, but from the Improvement editor screenshot:
http://www.apolyton.net/civ3/images/...dit6-thumb.jpg
it seems that abilities/effects are grouped by inmprovement type, and Great and Small Wonder effects are non-mixable groups. Therefore, using the given editors, we cannot make the Manhattan Project a Small Wonder (as it rightfully should have been, dammit dammit.)
I suppose there's a chance that it may be enabled somehow using the improvement editor, but I strongly doubt it. So, I'm wondering, is there any way to link units, advances and improvements in such a way as to require a Small Wonder be built before a civ can build nuclear units? The improvement editor shows that improvements can be linked to other improvements, govs and advances, so this may conceivably be done (though hopefully in not too convoluted a fashion.)
While I grudgingly understand Firaxis' decision to release the game as they did (nukes being so powerful that allowing all civs to have them around the same time levels the playing field a bit), they should at least have allowed for scenarios where each civ must join the nuclear community by themselves. I do, however, find it odd that each civ must conquer space individually, but the work of one civ allows everyone to bomb the hell out of each other.
Aside from this, I must admit that the game looks outstanding, and I'm heartened by early reviews. I do sincerely hope, however, that Firaxis stands by their statement that they are devoted to the mod and scenario community, and they open up many more of the games inner mechanics to us. We promise everyone at Firaxis that we would do you proud.