So for whatever reason I have this weird fascination with the Call of Cthulhu game, which makes me gravitate towards it as a system despite its flaws (which, to be fair, are in my view not worse than most other games). For once I think this may actually be a good idea.
Basically I was, I think, listening to some Miskatonic University Podcast or other which probably mentioned about characters being normalish people with no special abilities, and this either prompted or reminded me of an idea for changing that without completely overhauling the game.
I have so many game ideas thrown out and languishing unfinished that I've probably forgotten some myself, but I was talking about a thing called Alpha Dregs the other month and this is very tangentially related.
My new idea is very slightly like Alpha Dregs in that you have powers you can't really use, but differs in most other respects, such as the actual point of the game, which is to do the same stuff you normally do in Call of Cthulhu. This wouldn't be a new system, just one game run in BRP.
So basically the premise is that you're a bunch of people with poorly-controlled mutant abilities, more along X-Men lines than classic superheroes. Details don't matter hugely, but I broadly imagine that you're brought together either as a kind of Mutations Anonymous group, or by a small group of scientists, civil servants, clergy, social workers or whatever who are trying (and so far failing) to convince anyone important that this is a real thing that someone should be addressing. Picture the traditional frustrated public sector worker, trying to do their job in the face of job cuts and general indifference, only now they're trying to get someone (anyone) to believe in superpowers without getting themselves fired or institutionalised in the process, nor bringing the tabloids down on you poor folks.
For whatever reason the characters get drawn into weird stuff. Maybe they form an unlikely detective agency. Maybe the tiny barely-known department trying to take care of them also handles everything bizarre and they get dragged into it. Maybe they're on the way back from a meeting when a hunting horror grabs someone across the street. Maybe they're actually in some kind of facility, the place suddenly collapses and they have to help themselves. Doesn't matter.
I'd be inclined to handle this pretty loosely. I'd encourage players to give themselves, say, three new skills to represent their abilities, each one based on an existing stat (probably 2x stat) and able to increase as normal. Skills would be broad in scope and can be used however the player wants, though difficulty should be adjusted as seems appropriate. Each successful use of a mutant power would cost at least one Magic Point. Each failed use of a power costs one Sanity Point.
So Arthur Perkins is a mutant bank clerk. He ends up taking the skills Telekinesis, Force Field and Levitation because they seem like a coherent set. The group rules that Perkins can use Telekinesis with the distance acting as a modifier; he also uses POW rather than STR when using it, and a very good roll will increase its effect. Perkins can now use this to shut doors, interpose crates between him and nearby ghouls, or attempt to hurl said ghouls out of sixth-storey windows.
Lucinda Beversley is a mutant lady of leisure. She takes Pyromancy, Summon Elemental and Phasing as her powers. The result of her Summon Elemental roll will determine (amongst other things) whether the elemental will actually obey her, though only on a botch might it become hostile. The group decides that her Pyromancy powers don't create fire from nothing, but depend on some source of heat being available, and that turning a small heat source into a serious fire will be more difficult than simply controlling an existing fire.
My feeling is that this would be one case where the BRP percentile system's high failure rate would be fitting, as characters attempt to invoke unreliable powers and deal with the consequences. It would keep things fairly genre-appropriate while introducing special abilities to the game. Basically I think it might be quite fun.