I'm actually happy. Now knowing the combination mechanics, it appears any 3 bikes can combine (even if all 3 bikes are, say Chromia). So even if the 3rd bike's unique mould does not get produced but is rather just a repaint of either Chromia or Arcee, the 3 toys should still be able to combine. And if we simply rotate the 3 bikes, we get 3 possible different combined forms (6 if you count all possible permutations).