Bandwidth is not really an issue
, but costs are.
Over continental airspace bandwidth will definitively be if using conventional Comms links, which are already saturated with mode S data., outside VHF coverage you will need satellite comms.
Satellite comms are still very expensive because all privately owned or run , and airlines are rejecting the idea of mandating it. Been discussed already for years within ICAO.
And as Dave pointed out already, ADS B-Out is not made at all for this.