Downside to the ruins stuff is that it relies on having a large number of razed cities in your lands.
Haha, well, that's the point. Perhaps it will partially compensate you for having to fend off hordes of Monty's jags during the early B.C.'s.
Of course, if you can manage to do some early warfare yourself, you can raze a few and be sure of cashing in later on (well, at least somewhat sure...you could not open borders to be completely sure). A quechua-rushed city ruins from 3000 B.C., excavated around 1500 A.D., would be worth gobs of gold, beakers, and culture.
This would lead to some interesting decisions. If you knew, or if you suspected that a city ruins site was relatively new, you'd have an incentive to preserve the ruins for your national glory. But if you suspected that they were quite old, you could take a gamble and see what you got....
This, would require, of course, a small additional game mechanic of having the game keep track of how old city ruins sites were, or when a city was last razed on a tile. But how hard could that be to program?
(And, of course, this is in addition to the other uses of the Great Scholar: building a museum for +25% research and +25% culture for that city (perhaps the museum should require the aesthetics tech...), bulbing the bulbable great scholar techs, settling for a 5-beaker, 5-culture super specialist, or conducting a lecture circuit after researching mass media (hmmm...the more I think about it...instead of a one-time bonus for the lecture circuit, it would make more sense to be able to perform repeated actions in multiple cities with this great person, and get a small gold and culture bonus each time (like a bunch of mini-culture bombs...would be useful in preparation for an invasion--instant border pops!, like with using the "spread culture" function of spies, but even better). But, of course, you would not be able to harvest gold and spread your culture twice in the same city because your great person's ideas would not be so new and exciting. So you'd have to go around visiting new cities. You could either cap the number of visits at something like 20, upon which the great scholar is consumed (from exhaustion, perhaps), or, maybe have it so that you could go on doing this forever, and once you ran out of cities worth visiting (because the smaller cities without libraries, universities, and observatories are not going to give your lecturer much of a response or turnout), and assuming your great scholar did not get killed while conducting his journeys(!), you might want to, instead, then settle your great scholar as a super-specialist as a sort of retirement. This sounds powerful, basically getting two functions for one, but at this point in the game your super specialist great scholar is not going to be around for very long to contribute much after his lecture career is over. But you'd still get something, and it would make mass media even more of a tech to shoot for if you are aiming for culture--the ability to lecture-circuit your great scholar before settling him/her. And face it--late game great people are powerful in general with corporations. Great scholars won't have a corporation that they can found, so this is a little bit of compensation. This way, getting a late-game great scholar won't be like getting a late-game great prophet, which is just a wee bit obsolete and which you can only settle as a super specialist, unless you still have some holy cities that you can shrine.
Also, with the lecture circuit, you'd also have an incentive to not settle or use a great scholar immediately if you are approaching mass media. This also keeps great scholars relevant for the modern era because, after mass media, they won't have any techs that they can bulb, and they wouldn't be very good as late-game settled super specialists because of the payback time before the game ends (as with any settled great person), and museums might not have much time to pay off either...same thing with preserving ruins. If you are lucky, you might have some older ruins still laying around that you could excavate for a nice one-time bonus, but not guaranteed. So if all else fails, wait for mass media to lecture-circuit your great scholar. Also, if I saw my "ally" going around with a great scholar and spreading culture in my cities, messing up my cultural borders, and getting wealthy off it to boot, I might feel very tempted to close borders. Could lead to some funny situations....)
Edit: Also, I just thought: concerning excavations: the amount of one-time gold, beakers, and culture should also depend on how many libraries, museums (including the Hermitage national wonder), and universities your empire has that will enable it to use and decipher the knowledge you have. So you might build a museum with your first great scholar (because, with libraries initially giving great scholar slots rather than scientist slots, you're probably going to have a fair amount of early great scholars), wait for the old city ruin sites to mature a bit, and then with your later great scholars cash in on a better excavation.
Also: great scholars should be able to hurry the construction of the Hermitage. Not that that would generally be very useful. Just because it makes sense.