Kitbash advice

Hello friends,

I'd like to purchase some Assault Marines, Cataphractii and maybe some Tactical Marines from 30K to use as Raptors, Terminators and Legionaries respectively, for a Slaaneshi Night Lords army in 40K. I really love the models from Horus Heresy and I was wondering if this is a good idea? Also, any other models you'd recommend from 30K? I'm probably gonna include some War Dogs too.