^they already have Beast as their resident tech expert/genius
... The time machine* is designed in a similar way to Magneto's mutation device in the original film. The machine is powered by Mag's himself, and you could have a scenario that mirrors X1 where Rogue uses the machine to travel back in time by leaching the power from Eric (too frail and old to use it himself).
though, I wouldn't be surprised to see something like this, especial with Bryan Singer back in control, an it would be a neat little nod back to the first movie... but with that said it might feel like kinda of step backwards to basically recycle/retool the story from the first movie, instead of moving forward with something new an original