Let's says that the X-Men started to gather all members and non-members to fight and protect against any threat toward Earth. By doing that they form some sub-teams an additional of the main team that protect the following: Sea, Earth, Space, and Dimensional Threats. I know it sounded silly but anything can happen in the Marvel Universe.
Sea team: Namor, Sedna, Loa, Triton, Princess Len, Darwin, and Namorita
Space team: Havok, Beast, Abigail Brand, Warbird, Kid Gladiator, Polaris, and Ariel
Dimensional team: Cable, Pixie, Shatterstar, Rachel Grey, Forge, Frenzy, and Colossus
Earth team: Cyclops, Iceman, Psylocke, Magik, Gambit, Cecilia Reyes, Storm, Beast,and Wolverine