Having the laptop battery and cooling would be much better
Except WiFi modems are cheap because there is lots of competition and most of the patents are easy to license, so everything has WiFi now.
I was in Phoenix AZ last week when it was 115F and my phone’s hotspot shut down because the phone got too hot.
Yes it was awful.
Even plastic clad android phones will get hot if you try and make a long phone call from BFE.
Any phone can do that, not only iPhones. How often are you on the move without a phone?
Also the battery argument is not so definitive since a laptop on 4G/5G would also consume battery. If you can connect your laptop to a wall outlet you can connect your phone too.
https://www.cnet.com/news/apple-wants-its-3g-macbook-prototy...
(Green and blue boards tend to be for production-ready prototypes, red is fairly hacked together.)
I believe the objections are 50:50 software-related and battery. How do you set suitable data usage thresholds on a Mac which is running over a 3/4/5G LTE network? The thermal performance of MacBook Pro is already weak at the high end and battery life suffers.
I would be surprised if, when Apple switches to its own power efficient chipset in its portable Mac line, they don't offer a BTO option which includes cellular capabilities through a built-in SIM.