I think the iPhone pro has a thunderbolt controller which is an added expense. Can it support enough additional controllers to support all the ports that the current external case supports? Is it even an economic proposition to do so?
Don't think any iPhone has Thunderbolt. Apple Silicon uses on-chip Thunderbolt/USB4 controllers - I don't think it's public knowledge whether the A19 Pro has this (maybe not).
Still, Thunderbolt isn't mandatory on a "budget"... OK let's call it a Mac Nano. 2 USB-C ports (possibly on a hub) and HDMI would do it.
Should we expect it to support 3 external displays though? Will the ram on board be limited to 12Gb as the current iPhone pro comes with? Will that still support Apple intelligence in macOS?
You're assuming that a "Mac Nano" would need the same ports, RAM and display capabilities as a Mx-powered "full" Mac Mini. It wouldn't. Anyway, we don't know what capabilities the A19 Pro chip has - just what has been implemented in the iPhone.
And the a12x/z series was surely already an M series cpu in everything other than name. It had more graphics cores if I recall.
How is that different from the A19 Pro?
The developer transition kit didn't have Thunderbolt and ISTR that, at the time, it lacked a few instructions that the M-series gained. Didn't stop it being a perfectly usable MacOS machine for the brief period for whidh it was supported.
I can’t really see a market for a Mac nano using A series cpu. It would be an entry level sku in a line which gets very few sales as it is.
I don't disagree - I'm just saying that it would be feasible, not that it's likely. I think Apple could do with some better low-end options - I don't think Apple care.
Having said that - there’s already controversy over App stores lately.
Android (for the moment) still allows sideloading and alternative App stores/payment methods, yet the Google Play Store and Google Pay are still going strong. Even with the
option to use an alternative source most people will stick with the App Store to get the "footfall" - the profits might get a haircut but I doubt it will go away. On the Mac, the App Store has
never been forced on users, yet it is still getting custom. Plus, Apple services like Music, iCloud etc. don't depend on the App store.