Well I was being a bit flippant with that remark! Of course, if a human player were playing Mongolia with the goal of a CV and winning sporadic wars to boost tourism and strategically taking CS(s) with that goal in mind then all right , but if the AI is essentially playing a domination strategy and still being rewarded as if they were playing towards culture, then I say it's unbalanced. They shouldn't get to have their cake AND eat it too.
If I understand the tourism mechanic correctly, it should be reducing effective tourism by the # of cities up to a limit (maybe puppets don't count?). Also, this is only my best guess at what's happening..I don't know how to verify where they generated all the tourism influence. They only had about 30 tourism at Renaissance, but were already influential with ~10/14. They quickly culturally overcame an Inca civ with no North/South American rivals that had 36 cities of their own and were probably undiscovered for at least half the game 200ish turns - which seems broken.
I went with almost all defaults for the map 22 civs and 44? CS. Just wait till you see CS allies getting flipped instantly from halfway across the map with no Mongol military presence and then watch their tourism skyrocket - it killed an otherwise interesting game.
Suggestions:
1. Require border military presence to demand HEAVY tribute for all civs (not just Mongolia) - although this would fall unevenly on them. (This makes sense, because if you can't actually reach them, because you don't have open borders with a rival, then why the hell should they fear you..) I played an aggressive Turk game where I was able to demand heavy tribute from CSes 15-20 tiles away that I only sent an explorer to - it was definitely cheese.
2. Conquering CS should cause a negative tourism effect (which makes sense within the spirit of the game)
First of all, I'd just like to say that my first comment was just a question, not meant to flip you off or anything. Just generally all victory conditions should be open to everyone. Just wanted to make that clear first. The AI pretty much decides on a VC to pursue based on their flavors and a bit of randomness and they go for it as well as they can. That being said, VP is designed so that going for any VC helps build upon the others as well, this was partially designed to counter the fact that most people just ignored Tourism in vanilla because they felt it was useless. And it makes sense doesn't it? In vanilla conquering cities helped with all aspects of the game other than tourism for some reason, more cities meant more science, more cities meant more gold (or in this case more paper) to bribe city-states, and more cities meant more production. Now it also partially increases your tourism and your culture output, although having a bigger empire also makes you more vulnerable to outside tourism, especially if you neglect infrastructure.
I'm not exactly sure which gamespeed you are playing on, but turn 468 sounds pretty late so it would make sense the game ended around that time, wouldn't it? I mean one of the major flaws of vanilla was that the AI just never tried to win, they just attacked their neighbors and then just sat there waiting for you to build a spaceship. In VP if an AI have heavy advantages and you don't decide to directly counter it out it is going to win the game, either by culture or by spaceship.
Second, Tourism is reduced by the number of cities a player controls, in fact you get a percentage bonus to tourism based on the difference in number of cities between you and the civ in question, and the other way around as well.
Third, the Mongolian heavy tribute mechanic requires heavy military presence just the same way that heavy tribute requires for other civs. It is close to impossible to do without having any units close to the city-state in question. It is definitely an annoying mechanic to deal with, but I wouldn't say that it breaks the game or anything like that.
Fourth, as you mentioned the game isn't exactly balanced around those extremely oversized maps, everything from happiness to military scores to culture output goes a little bit whack when a civ can settle 50 cities no problems. I'm also guessing this is part of the reason why you were having problems with Mongolian ranged heavy tribute, a 50 city empire would enable to him keep such a big standing army that he could demand tribute from far away, at least in theory.
Fifth, tourism mechanics have already changed quite a bit since this version (as has tribute demanding actually).