Of you want something like a irk you should look into a lighter outer rotor kit, ooracing have some nice ones with lighting coils
https://www.ooracing.com/store/index.php?_a=product&product_id=2997
https://www.ooracing.com/store/index.php?_a=product&product_id=2999
This will be a mad build.
I need one of those bbr perimeter frames in my life, where did you get yours from mate, bbr's online ordering is currently down, also what rear wheel setup is that because i love the look of that monkey bike rear disk