Finally got around to trying out this civ, I have yet to complete it as I had to restart because you apparently can't steal a religion and add beliefs to it, you have it found it yourself to be able to steal religious beliefs (so no stealing byzantium's religion like I had hoped lol.) I'll update this post when I complete a playthrough.EDIT: You can't steal byzantium's bonus belief.
Final edit: still haven't finished my playthrough but I've basically won and I'm in modern now so I think I'll post my thoughts about the components.
UA:
By far the most intruiging and fun part of the civ, and amongst the most fun to use out of all the base/modmod civs, with only a few nitpicks about it. Being able to steal policies and beliefs was great fun and added an interesting religious focus to warmongering wherein you'd want to actually try and conquer central states rather than easier shore states (oval map, huge size) to make spreading easier. One criticism is that I found it limiting that you could only steal one belief, which is sensible balance-wise but I enjoyed it more when I disabled it. Also, there was the two issues I mentioned above but those are just nitpicks and don't really detract from the UA. The reduction to missionary power decay and increased pressure from trade routes are great and serve their purpose enabling overwhelming spread very well, but I found the faith per trade route too low at 2 faith (epic speed) per route to be noticeably useful when shrines are cheaper, quicker built, and don't need military investments to protect like traderoutes.
UB:
It's fantastic. Being able to relocate trade routes much more often makes converting cities so much more convenient and faster paced prior to open borders. It being placed at engineering is also perfect as it plays perfectly into the classical-medieval warfare playstyle that is optimal for kushan snowballing. It's also a nice little faith compensation for a civ that would otherwise heavily consider rushing temples/religious wonders, making it so that there's a real hard choice between rushing military or temples, which is a great design choice.
Mounted UU's:
Both are very simple but are useful for guaranteeing access to the strongest mounted units of their era for two eras in a row, with the knights being able to contest fairly tercios well too. Their simplicity is compensated more than enough by how uniquely designed every other aspect is and how they fit nicely into the optimal playstyle of the civ while not shoehorning them into warmongering like the legion would for Rome.
UGG:
Left this one for last because it's the hardest to make out for me. For starters the happiness is nice and would probably fit perfectly for a standard sized map. I found the kararaggo to be underwhelming though for two main reasons:
1. The double attack is something that is hard to utilize in any offensive situation because of how it rewards keeping your range units on a single tile to be utilized. It does make sieging a lot quicker and lets you level up your siege units much faster, but I don't think it's enough to justify weakening the frontline swordsmen whereIN 15% CS is enough to make a huge difference in how many turns your units can last on the frontline. Despite this it's very powerful on the defense but that goes contrary to the intended playstyle, and frankly is only really better than the 15% in a defensive circumstance if you're outnumbered substantially.
2. It's just really expensive. I forget exactly how much it was initially but it was difficult to justify even purchasing the first general, let alone the second and third which would take a huge chunk of infrastructure/military gold spending for relatively little utility.
I'm no designer but I think restoring the ability to earn the GG's through warfare, and maybe giving 1 extra movement on the unit under it would go a long way to making it useful enough to surpass the default great general.
Overall it's a very focused and fun civ that I'm definitely going to replay, with the only sore spot being how the Kararaggo is almost a downgrade to the default GG, but interesting enough to make it not much of an issue.