Funny how all that extra heat - which hasn't been an issue for the last 15 years - suddenly becomes an issue even though Apple Silicon consumes 2-3 times less power than the Intel chips it is replacing.
If the fan is roaring in your Mac Mini it is because the Intel i7 space-heater running it is putting out the thick end of 100W. The small fraction of that being wasted by the power supply is a drop in the ocean.
It's almost as if people are making stuff up to try and rationalise what is really a pure form-over-function (probably with a dash of cost-cutting) decision by Apple.
Even if the form-over-function was appropriate for the entry-level iMac, the worry is that it will bleed over to the higher-end machines.
The minimum power requirement for a Thunderbolt port is 15W and as far as I know, that's all the ports on any existing Mac will deliver. You can deduce from the power ratings of existing Macs that they don't provide 100W per port - e.g. the Intel Mac Mini (4 x TB3) is rated at 150W max (and the Intel i7 CPU was 60W average), the new 24" iMac (2xTB3, 2 x USB 3) at 143W. Doesn't add up - and remember the iMac has a fairly power-hungry display.
Consequently, the vast majority of USB-C/TB3 peripherals either run off 15W (or less if they are just warmed-over USB A devices) or require their own power bricks. The higher capacities are really only for powering/charging laptops.
So although Apple could decide to add TB charging capacity to new machines, they haven't done it to date, even with the new iMac, and while it would be cool to be able to power/charge your MacBook from your Mac Mini, it doesn't seem like a high priority.
What on earth for?
The internal power supply in the existing Intel and M1 Minis is already slightly more powerful than the iMac (150W vs 143W) - justified in the Intel version where the processor TDP (i.e. average) was 60W and probably only kept in the M1 version because Apple didn't bother to re-design the power supply for what is probably only a transitional machine.
Remember the iMac power brick has a large, bright display to drive, too.
If you really want to remove the PSU from the Mini, the next most sensible thing to do would be to make it TB3 powered so it could run off a TB display or a powered TB3/4 dock with your preferred selection of ports.
History lesson: USB on the iMac replaced a bunch of Apple proprietary ports like ADB and LocalTalk and the technically standard RS423 serial that was just different enough from the widely used RS232 to be a headache. It also replaced lower-end applications of SCSI (huge cables and connectors, termination issues, device-ID DIP switches, "enterprise"-level prices...) which was limiting the choice of affordable scanners, zip drives etc. to what were becoming effectively Mac-only products.
USB ports had already started appearing on PCs - where RS232 and Centronics were already past their sell-by date - MS just needed a nudge to fix the Windows drivers. A year or two after the iMac came out, there was a good choice of USB printers, scanners, mice, keyboards, hubs, modems, external drives etc. at attractive prices because they were no longer Mac-only. It was a major step forward. Which is probably why everybody stopped whining about it within a year or so.
(Oh, plus, at around the same time as the hermetically-sealed iMac, Apple released a G3 tower which set new standards of tool-free access to the innards, with space for user-replaceable drives and expansion cards... Jobs' Apple wasn't obsessed with sealed boxes: they just understood the difference between consumer "appliances" and professional tools, and designed each accordingly...)
Problem is, although the downstream Usb4 ports don't need to support 100W per port, they do need to support 7.5W per port (rising to 15W for TB4 branding) while being connected to a single 7.5W or 15W upstream port (which is all the vast majority of hosts support). So there's a niche for a totally bus-powered hub (or one with a smaller ~30W brick) - but for laptop users it probably makes more sense to use one with a beefy power brick that can also replace your laptop's charger.
...sure, but you've countered your own argument: you can already put a 27" iMac Pro in a flight case and wheel it round. The new 24" even more so - but it's still going to be a pain to carry around (given that you can now get almost the same performance out of an Apple Silicon laptop that fits in a manilla envelope) and making the body ~5mm thicker isn't going to be the straw that breaks that camel's back. Plus, d'oh! weight-wise you're still going to have to carry around the power supply and any other gubbins that Apple have made external to save weight.
...and needing a second rack for the power supplies (to which all the ethernet cables would be routed) would make it harder. Yes, if you are running several racks full of Macs then the power supply failure rate might be significant - but so will SSD and other failures so - given that Minis are relatively cheap - it will probably be more efficient to swap out the whole unit.
I suppose you could make a custom power/network distribution unit - if Apple will license the new proprietary connectors - but if you're going to go that far, why not crack open the Minis and extract the logic boards so you can build a dozen of them into a 3U rack case?
Of course, what would be far, far, far better would be for Apple to release a proper rackmount server - no, not a Mac Pro kludged into a massive rack case, but a proper rack-format 1-2U server (or blade system) with lights-out management, redundant power-supplies etc. I think the XServe died after the Intel switch because it offered too few advantages over generic PC kit to be worthwhile - with Apple Silicon, Apple have a unique offering again (and, frankly, sticking an Apple logic board in a generic server enclosure designed to power and cool much hotter processors ain't exactly the Manhattan project R&D wise...)
