As a Street Fighter-head.... I understand what he's wanting to do.
The main issue is that console versions of Super Street Fighter IV had DLC updates to the next release in the series, Super Street Fighter IV: Arcade Edition (and then a free DLC update to v.2012). Arcade Edition added four characters (Yun, Yang, Evil Ryu and Oni), and v2012 was a balance update to the 39-character cast.
Thing is, I'm not so sure that's possible, since they very likely downgraded the models for 3DS (as it was a launch title, and thus couldn't push the hardware very hard). You'd have to do a lot of work to make the 4 (9 if you try to hack to Ultra instead) new characters lose enough geometry to run well on the hardware.