Much of this is able to be done with wifi, but not via the cellular networks (without additional costs).
In other words, there is no ideal one-size-fits-all option, and I'd be willing to pay for additional hardware to give me choice of what to carry at any given time, but I do not want to pay Verizon just for the privilege of having a 2nd SIM provisioned (and I do not want to swap SIMs).