Imagine they actually made a movie about Rebecca instead of an episode, Suzie finds Rebecca broken Just like Thomas found Hiro Broken, same reason, broken brakes due to a contest of strengh. Nia would still be there as she was on the island before. Spencer would build another summer house, this time away from Hiro's hiding spot, instead near Rebecca's. Here's part of the line...
Narrator: Then there was trouble, Spencer sneaked onto the tracks behind Suzie.
Spencer: Found you Suzie!
Narrator: Suzie's wheels whirred like the wind.
Spencer: you won't get away from me this time!
Narrator: Rebecca chuffed as fast as she could. she wanted to wheesh away from Spencer, then Spencer saw Rebecca and gasped. Spencer had never seen an engine as strange as Rebecca before.
Spencer: Who are you?!
Spencer: That engine can't even puff properly!
Think of what patchwork parts Rebecca could lose.