I am a recent convert to BRP. Although I played some Call of Cthulhu back in the 90s, I have been pretty much exclusively playing D&D 3.x/Pathfinder for most of the last decade. What brought me back to the d100 system was a desire to get away from the medieval superheroes games that inevitably result from the class-and-level design. While BRP is a great game, I can see how it might be a bit intimidating for new players. The BGB is a monster, with far too many optional and alternative rule systems. Contrast that with RuneQuest II by Mongoose, with its tightened up rules and I could see a new player with an interest in the d100 game engine choosing MRQII over BRP. I chose the latter because I already had some famiarity with the system and I really wanted a generic game, but I suspect I may not represent the normal profile of a potential new player. So one thing I would suggest that might help BRP is a streamlined version of the rules, more substantial than the free quick-start game, in that it should include magic and psychic powers (though not necessarily mutations, sorcery or super powers), but less weighed down with optional rules.
I think the imminent arrival of Chronicles of Future Earth is also a step in the right direction. Unlike CoC and RQ, BRP doesn't really have a signature setting. There are a lot of monographs and many of them are quite good, but I think a supported setting with multiple supplements helps a lot to inform gamers of what a game system can do. I know from my own experience that it was my interest in CoFE that drew my attention back to BRP.