I2C read/write request would benefit (and allow a larger bytecount per write-message which is not just a performance-, but also a functional benefit). The same for STRING_DATA (if being used frequently). The other 'larger' messages (Capability, PinState, FirmwareNameVersion) are usually one-time/startup only so they have litte implact on performance.
shift- and pulseIn/Out will also benefit from this (which is not a backwards-compatibility-issue though)