I see Green Ronin is developing a new system. It is called Sword Chronicle, and seems to be a genericized version of the Chronicle system that they used for their Song of Ice and Fire Roleplaying.

One notable aspect that may adapt well to Birthright is that your character belongs to a noble house, status as a statistic, rules for both individual and mass combat, etc.

https://greenronin.com/blog/2020/07/...ord-chronicle/

Could be interesting.

-Fizz