Hey! I really like the idea of making this character real, looks quite badass. I have an eye for kitbashing and had a few ideas if you don't mind trying them out
Anyways, I instantly recognized that the legs look extremely similar to the Darth Maul legs without the skirt. With some brighter boots, it'd look pretty spot on maybe minus the bit of armor on the feet.
https://gyazo.com/b458c288bbbe6d76f96beb27c9da4efa
As for Ren's skirt, I instantly thought of the KOTOR Jedi model. That made black with perhaps some padding from this Samurai model from mrwonko.de and it'd look dead on.
https://gyazo.com/a1e9cc0b347847b6dad30e6343a7f3e9
https://gyazo.com/387219bcc16642491654c0676702f086
The belt looks nearly identical to that of the TFU version of Darth Sion, which someone ported, so you could use that.
https://gyazo.com/71ef4c524d38e324fa19f2ed1a1c2b2b
And then there's the mask... I was thinking a retextured Jedi Temple Guard mask would work excellently.
https://gyazo.com/4a2c19aa71049de1266ac0f2c8803859