Cool models/conversions/'counts as' has never been rejected at the OFCC (unless the list was excessive, which in my experience hasn't happened). If you want to do a cool conversion army with an awesome theme, then by all means go for it - just count them as Boyz instead of Savage Orcs and BAM!...problem solved. If someone is more interested in the modeling then don't use them as the power unit, go for something tamer.