That’'s why I suggested Daqrk or Feudal.
There. So, if one unit can have a pre Castle Age access, why can’t one more. I understand that maybe Serjeant is a pointless unit because all it does is creating and repairing Donjons. Other then that, it’s similar to Militia line than to Woad Raider/Huskarl type. Ratha, however (in my opinion at least) will be viewed differently and will be liked by a lot of gamers.
Yes we do, but through patches and DLCs we can address that too. I’m not demanding Conquistadors and Janissaries to be moved to the Imperial Age and strip them of the Elite status (although, that might actually work, we done that with Thirisadai).
And besides, we also done that to the Indians UU, the Elephant Archer. We gave it to all Indian civs and gave Hindustanis Ghulam instead. No complains there. Neither there were any for Thirisadai and Serjeant (that is until they got balanced, but this is a common strategy of every patch and DLC: Add new civs and campaigns, disbalance the game a bit, hear some ideas from us, issue a patch, rinse and repeat).
It was possible with Serjeant, so I can’t see how hard it will be, besides devs know how to program, we just toss in and discuss ideas here (some of which, I agree, aren’t successful).
As a side note, as somebody already pointed out in a separate discussion, proposing Bombard Cannon Elephant. However, unlike the previously proposed version, this one will replace Ratha as a Castle Age UU. Furthermore, I didn’t thought of that earlier since balance is something that I tend to ignore as you all see, but maybe putting Ratha as a Dark Age/Feudal Age UU will be beneficial with a chance to upgrade it to a similar Stable or Archery Range unit in the Castle Age? Like maybe a sword/bow and arrow dual wielding unit? Will be blanced if done correctly, again. 
Thoughts?