6) Excalibur
From the Comics: When the X-Men were thought dead, former members Nightcrawler, Shadowcat and Phoenix found themselves in the United Kingdom, and teamed-up with two of the local heroes, Captain Britain and his girlfriend Megan. Captain Britain has superhuman strength, speed and the power of flight as granted to him by the wizard Merlin, while Megan is a shape-shifter, and together with the former X-Men they decide to protect Great Britain from any potential evil that threatens it.
Connection to the Film Series: Both Nightcrawler and Shadowcat have been introduced in the film series before, played by Alan Cumming in X2: X-Men United, and Ellen Page in X-Men: The Last Stand and Days of Future Past, respectively. If we’re going to get really inside baseball, Psylocke, one of the new mutants to appear in X-Men: Apocalypse played by Olivia Munn, is actually the sister of Captain Britain.
[zergpaid]Adaptation: Nightcrawler hasn’t been seen since X2 (although he will be seen in a young version in Apocalypse next summer), so it begs the question as to what he’s been up to ever since. Maybe he made his way to Britain and found another group of mutants, perhaps assembled by destiny, to protect the British Isles from the threat posed by evil Euro-trash mutants. There are more than a few X-Men characters that hail from England, Scotland, and Ireland without having to wonder the question of “who owns the rights to Captain Britain?”, so it should be easy enough to put a team together. And on top of it all, with the mythology behind a name like “Excalibur,” there’s another whole franchise potential for Fox if they’re interested.