For the majority of the life of the board posters have mostly featured and promoted their own characters. This was particularly true in its earliest phase, where there were regular issues of Jarvis, Fin Fang Foom, Dynamic Donar, Abandoned Legion (by spiffy) and others. All featured their own casts, although some characters from them have now become commonplace across others' writing - Hallie for example.

I think the key to using one's own characters rather than a "world's greatest" team is to tailor the adventures so that only that cast could enounter that plotline and deal with it in that way. The X-Men's traditional - and very popular - niche in the Marvel universe is in dealing with mutant-related, rejudice-themed, and sometimes educational-based plotlines. They've done it so successfully as to generate a whole sub-mythos where Iron Man or Daredevil would feel like trepsassers if they were thr first-call heroes.

Taking that thought further, look at what you're working with: You have a world-famous hero who few people have heard of with cosmic-class powers; the world's foremost cyborg who runs her own detective agency; an off-the-books ninja; and a black-books project android. That immediately suggests international espionage, some tech-related storylines, a dash of offworld adventure.

I've been encouraging you for some time to generate a world-class villain who's specifically going to clash with these characters, for whom they'd be the first-call heroes. He or she needs to have personal ties to them so there's an emotional element, and to be sufficiently different from existing major baddies to occupy a unique niche. The mere existence of this character would drive some adventures and require your cast to assemble and interact. Looking at your cast, I think a male James Bond-style villain might work best; but someone with sufficient physical capacity to prevent any of the heroes from easily besting him.