Is a regulator necessary?
If they run all from the same battery, and no analog circuitry involved, no problem. The LoRa has its own built-in regulator if the module has a wide-range power spec.

No, I don't see why it shouldn't work.

The con of a regulator is size and heat created on one spot. Well, the latter even may be a pro if you have to include a heatsink of some sort anyway.