One of the most interesting event in the game is assuredly »the combine«:

»Prohibit«, giving a +1 to the city cap, while coming quite late in the game, can still be very valuable.
But »Wait« looks really like a bad joke.

I'd suggest to modify it into:

give +5% fame.

I thought about 5%, 10% and 15%. 

Considering the generation of fame of the player:

1. If they do not build a new city, it is a boost towards generating influence. Influence counts for 1 out of 7 or 8 with TwR star groups. If you add the affinity, count 8 or 9. So it'd be mostly a boost on 1/9 (go buy the DLC, it'll help me write simpler post, thanks) of the stars, close to 10%. However, it does not start from nothing, and will most probably not account for even the half of your production, making 5% maybe even a bit generous, at least better than the city cap increase.
   
   
2. If they build a new city, the question is to assess how much it'll help increase the player's fame. [I'm looking at a peacefull play, as warmonger tend to be so much above the city cap, that it doesn't really matter if they're stuck at +10 or +11.] If they made the small council choice, they'd be at 6 cities already. This making it the 7th. As everybody is playing at +1, +2 or +3, they'd have in fact between 7 and 9 cities. A new one would then be the 8th to 10th. Making it more valuable, we'll play with the example of the 8th city. It represents 12.5% of the player's city but will not provide that much for stars.
   1. Expansions stars are a bit independant. One might add that it'd cost less to add some territories to an existing city than to create the 8th, granted, it might be tough to attach territories if they're too far... and that assimilating a city state can also grant you peacefully a new city.
   2. Agrarian star will be the best an easier to get, especially with the horse infrastructure and some horses to go with. It'll actually increase faster than in other cities.
   3. Military wise, however, the new city will be too small and produce too little for some time.
   4. Influence, Research and Money generation will also be quite low.
   5. Districts might be easier to build at first, giving a boost here.
   6. Diplo stars seem to be quite independant from those shenanigans.
      
      So we got really to star groups that will benefit really the player in sensible ways but still not enough to account for all star progress. Would that even match a 5% fame boost? I'm honestly not sure, even if I wanted at first give it more than 5%.
      
      

A bit messy, sorry for that, hope someone can nonetheless exploit my thoughts.

I'm not sure always about the timing of the event. Sometimes I feel it comes relatively early (classical or medieval?). Or maybe that was in an earlier version of the game and now it comes later. Anyway, I like that there are more opportunities for get more city cap.

Regardless of early or late, % fame is probably better. Usually fame comes as a minimum of 50-100.

Yep I agree that 15 is too low, perhaps i will say 150-200? 

Still feel too low to be a real alternative to the city cap option.

It should be something else that has a huge impact like +2 CS or free tech

Cure_off wrote:

Still feel too low to be a real alternative to the city cap option.

I always found city cap was low when I compared to free fame ^^

It can't be a very important reward either, because I don't have the event on every game, and I'm not sure every player in a multiplayer game will get the event.

Well, if you don't need the city cap, because you stay below, or you're only at +1 and do not wish to go to +2, yeah, it is pretty useless.
But, if you are at +2 or +3, the simple bonus to influence is, in itself, enough to probably get one more influence star. Even if it is only the first, it might be worth around 100 fame.

It can be deactivated in MP or maybe made sure to pop for every player.

Diegoyya wrote:

It should be something else that has a huge impact like +2 CS or free tech

CS is not always useful, nor is a free tech welcome. Fame at least is always something you want.

I do like the idea of a fame multiplier (+5% or +10%), and to be clear, not a retroactive boost on your existing fame, but a boost on future fame like the Singaporeans and the Great Mosque of Djenné.

Any idea what happens if you wait? I picked that and nothing happened for a while so went back and loaded the save for city Cap. With 11/6 cities my influence was taking a massive hit with the -1500 city cap. Frustrating.

Wait just gives you fame