To win diplomatically you only have to build the UN and not sign any MPP's. Thats just about it. Nothing else you do in the game is very important, as long as you don't go out starting wars. Building the UN is very simple. Even if you don't have a leader, just have a palace being built a few techs before and you're guaranteed it. Every AI will at some point get drawn into a world war, alienating most of the other AI in process. Even if you make 1 or 2 Civs mad at you, they probably will just abstain from voting. The tech to build the UN (Fission) comes well before all the spaceship parts are available, and the cost of the UN is much less than the combined cost of the spaceship parts.
It's relatively easy to get a Diplomatic victory on any difficulty level, and not have to "play" the game at all. I've built one city, never researched a tech or fought a war, and still won diplomatically in the 1600's on Emporer/Small map. My score was around 2000, which was more than that game was worth no doubt. Adding the bonus I described would have given it another 6000 or so points (~400 * 15). Game took all of an hour to play, with most of that waiting for the computer to process the AI's moves. On the same map, that would have beat all other types of victories, except an early conquest. Even if I had expanded and done some of the researching myself, it would have
slowed down the overall tech advancement. Granted that on other map settings and difficulty levels this wouldn't always be the case. On a larger map though, I probably would have won sooner. The AI did all the researching, and would have had more cities to do it with. For the most part, giving a bonus to Diplomatic victories wouldn't reward skill at all. In many cases, well played diplomatic victories would score less than poorly played ones.
Cultural victories aren't too difficult to achieve, but it does force a player to at least expand and build, and most likely fight a few wars in the process (have to have 2x the culture to win if not a 20k one city victory). OCC cultural victories are very much like the Diplomatic ones, but don't really matter that much since they are only possible in the late AD's. I'm not sure, but the earliest a OCC cultural victory would be attainable should be somewhere around the 1800's. Compare that to 1500's for OCC diplomatic victories (on higher difficulty levels). A OCC space launch is actually a pretty difficult thing, I haven't heard of anyone doing it on deity yet. Probably the only way would be to get several leaders, which would require a lot of warfare (very dangerous on deity and OCC). In any case, it would also not be attainable until after the UN had been built for quite a while, and would at least require one facet of the game (warfare) to be played.
Bloating, or Milking, a game for more points certainly doesn't take much skill. Getting to the point where it is possible at least requires the player to work a bit, and with the scoring bonus I'm talking about, it would make the scores relatively even for winning early, or building up to win late.
I'm not saying that diplomatic victories can't be played skillfully mind you. Just it
can be a very easy way to victory, requiring little to no skill, and the score wouldn't know the difference. So if we adjust the scoring to allow well played diplomatic games to compete with other victory types, then we run the risk of having poorly played games beating more deserving ones. If the # of civs was low (2 or 3), and on regent or below, then the differences might show up more. Of course, if anyone ever obtains a Diplomatic victory with only 1 AI opponent, they deserve to win
