That's why I suggested a bump to mountain UA values and a starting bump for the TF (prolly add another culture or another food to it).
I'm going to repeat myself again, not because I think I'm the one deciding, but because I think the matter is important enough.
I think the main failings of the current Inca design is the heavy reliance on mountain-chains. Grouped up mountains buff each other giving you great yields, grouped up mountains tend to create huge terrace-farms, supporting huge population-growth. Big mountain-chains gives you a lot of room to maneuver and flank your enemies, and makes your ability to build roads and cities on top of mountains really powerful.
If you end up spawning near a great mountain-chain then the Inca works perfectly well as they are currently designed, a few well-placed sheep are going to make people angry, but in general they are going to reap powerful advantages and have a good game.
These situations are absolutely not in the need of a buff, they are doing great. These are also the situations that would benefit the most from your suggested changes, sadly enough.
As it is however, you definitely don't always spawn near a big mountain-chain. You usually spawn near one or a few mountains at the very least, but solitary mountain-tiles are close to worthless with the current design, they add an extra point of food to nearby terrace-farms (usually one or two viable hills near each mountain) at the cost of a lost workable tile (1g 1f is definitely not worth working). Two tile mountains are better, two food and two gold tiles are useful until you can farm your grasslands or build a lighthouse in a coastal city, you can also usually fit a terrace-farm adjacent to both of them. In the end however in both these situations your UA and UI are clearly under-performing.
These are the situations that desperately needs help because these are the situations most AI are going to find themselves in, as they don't have access to the restart-button that players have. Yes I understand that the Inca are supposed designed around mountains-chains and hills, but this is just too much focus on a terrain-type that is way too uncommon.
Compared to for example river-based or forest/jungle-based civs, actual mountain-chains are just not common enough. And even for the Iroquois which can be considered the closest to the Inca in terms of design (forest/jungle instead of mountains of course) people are complaining about the design and about the inherent weakness of too narrow focus.
Other terrain-dependent civs usually have things that work independently from their terrain-dependence:
Netherland without rivers have their UA
Maya without forests/jungle still have their UA
Brazil without jungle still have their UA
Askia might have a problem without rivers, but his UB isn't that horrible, rivers are pretty common and he is excellent at conquering cities located near rivers.
Are sexysheep sheep next to mountains, or are we talking about the kind of sheep that seduce scottsmen? =|
It's a script in the map-generator that adds sheep when there isn't enough food in an area (and mountains/hills are known for not having very much food)