Guess we should count our blessings that 7-bit bytes didn't become the de facto standard. Given that 7 bits is sufficient for ASCII and BCD, and the popularity of the IBM 1401 in the 1960's, that's not at all implausible. The alternate history might have had only 2^28 (268,435,456) unique IP4s. The cynic in me wants you to be sure to include the inevitable "We'd be better of with 10-bit bytes" headline in the 9-bit alternate history.

I've always taken it as a given that we ended up with 8-bits bytes because its the smallest power-of-two number of bits that accommodates ASCII and packed BCD. Back in the day, BCD mattered rather a lot. x86 has legacy BCD instructions, for example.