If each machine has a built in SatCom, then number remains the same unless the unit is changed so where's the problem with regards to phone numbers? If the unit is changed due to fault etc. then all those required to be informed would be informed......
Channel 0 seems to work most of the time with long-range being the exception and then SatCom can be used.
Taskings can and have been received by SatCom direct from ARCC, I see no problems with the exception of unit failure but that happened often enough with HF units where tx were strength 2 on a good day.....
Nothing against HF, to have both would be ideal but not having HF isn't a show stopper.