Would be surprised by that as we officially fly allready VNAV departures (VNAV armed on the ground) which is only available from 10.8 on. It was introduced with 10.8 and never retracted unlike the FMC version which had to be downgraded to 10.7 as 10.8 had pretty dangerous bugs. Reasoning not to retract the VNAV thing was mainly that 10.8a was to be delivered ASAP, however it never was.
Fleet commonality doesn't really play a role in my company, we fly around 15 different configurations of 737NGs at the moment.