I'm gonna say right now that it probably won't. That Haunter seems to be in the common form of MDL0 -- the one that just so happens to be
not compatible with Brawl. It's the same type of MDL0 as used in Castlevania Judgment, New Super Mario Bros. Wii, NiGHTS: Journey of Dreams and Tatsunoko vs. Capcom, to name a few... which means that Kentilan's BRMDL viewer can open it.
Heck, I tried to put Bowser Jr.'s model from NSMBWii over one of the Alloys, and it froze every time. It's just not the right format. If only there was a way to convert them. I mean, they should be similar enough.