I wouldn't think they'd want to return to that flawed design - the trianglular thermal core required a pair of balanced custom GPUs which effectively became the bottleneck because I believe that they had to scale with the CPU and that never happened. And they charged for 2 mediocre graphics cards that were of limited utility outside of a specific group of users after GPU compute.
You could argue that Apple have continued to go that way by selecting high end W3xxxM parts in the 2019 Mac Pro - catering for a minority of users - some of whom have already jumped ship to Windows workstations.
If they have truly learned their lesson Apple would surely just create a box that would let users upgrade a standard PC graphics card to one that users could upgrade themselves but they just prefer users to take responsibility for their own external upgrades via Thunderbolt 3 - which is fine if it weren't for the massive cost.
For a 'pro' Mini, Apple would be better off taking inspiration from something like the
Ghost Canyon NUC. I'm not saying they do anything as small as that - or the way they decided to do it, but clearly something a fraction of the size of the Mac Pro containing just one slot - a 16x PCIe 3.0 slot which is electrically 8x - to fit a compatible off the shelf AMD GPU would be adequate for many. Size wise it could be a multiple of the Mac mini so the Colo guys could conceivably accommodate it.
To prevent the nickel and dimers from latching onto it Apple would sell it with 32Gb RAM, which users can replace with 64 or 128Gb if they wished, and 1Tb SSD (which users will have to accept can't be upgraded unless via BTO before purchase), throw in a decent 5500XT GPU at the very least, and price it significantly north of $2.5k. That's the Mini Pro as I'd like to see it - take delivery and start using it immediately rather than have to consider a poverty base spec.
That way, people who wanted their headless pro Mac are effectively pre-paying for a selection of Apple upgrades at their prices. If the screaming masses were right then it'll fly off the shelves - largely because it's the box they wanted but you have to pay visible upgrade prices to get it.
The point of this box would be to squeeze in easy to replace standard PC components - graphics card, ATX PSU if possible, SFF at a pinch, RAM, and ability to replace entire motherboard easily.
And before the fan boys start screaming about their own pet peeves - that's roughly the cost of a similar spec Mac mini maxed out accordingly but the one thing everyone in the mini forums is asking for is a larger case to help cooling. If you're already making it a bit larger then why not make it big enough to accommodate a standard graphics card and make it viable for users who are balking at the thought of doubling the cost of their cheap Mini just to get better graphics on it?
Anyone spending $2500 on a Mac with no display while studiously avoiding an iMac at the same price should be assumed to have an idea of what they are doing in my opinion.
Floating back to the topic at hand, the iMac is a perfect candidate for going to ARM sooner than the Mini because of the screen in my opinion. A cooler running all SSD ARM setup is a much better pairing with a thinner iMac enclosure in my opinion.
