Wasn't this version of Cerebro created/modified by Forge? I remember a scene, probably from HoX/PoX, where Xavier asks Forge to create it. So, while it is a technology, it is still created thanks to mutant power. And maybe Cerebro is also just for show, like the Five, i.e. it is important, but not the key component and only used to mislead people. Maybe there is some hidden mutant with power like super-memory and all "back-ups" are kept in its mind. It is just strange to me that Xavier now always wear Cerebro, such an important part should be well-hidden and kept under tight guard, but he instead publicly wear it, as if he wants people to notice it.
As for the Five, they probably should have several contingency plans in case something happens with any of them. One of the plans could be to use shapeshifters like Copycat, who could copy not just appearance, but also powers. So, she should be able to replace any of the Five in case of need. And it can go even further, if someone like Rogue or Synch use their powers to copy Copycat's power and combine it with Madrox's powers - they then would be able to create five duplicates and transform them into a perfect copy of one of the Five. Speaking of which, such line up could have been used to greatly increase number of resurrections, if several duplicate teams were created and were working simultaneously instead of only the original Five.