Serialise ISA... like a PCIe version of ISA.... but actually make it a bus, like I2C or RS485... that is completely transparent to a retro system, you have a single riser slot motherboard, you plug the adapter in and have 4 slot or 8 slot backplane, OR individual slots that connect to an octopus like USB hub kind of thing, use USB cable and sockets maybe. Maybe steal half of the USB signalling protocol to get chips to abuse. Anyhoo, you could then have a pack of cards size 286/386/486/pent motherboard that connected to ISA like this and you'd be able to build systems into any shape case. You could probably also fiddle with an ISA card on your workbench plugged into a system 10ft away, but IDK how much of a selling point that would be.
Okay, so everything later would probably need drivers to use the adapter over a PCI or PCIe... or whatever is in the future bus, or USB 2.1 up, or firewire.... whatever the heck bus you want to build adapters for, and also you can build shields for Pi type boards doing emulation and have an ISA bus that you can plug in.
Anyway, list of things it would do would be; ISA extender and risers for vintage and retro systems add several slots, while being very flexible in layout, Add ISA to PC systems without it now and years down the line, Add ISA to emulation systems, Add ISA to non x86 project boards to use cards in new ways.
Yes there are highly individual and pricey solutions for all of these use cases, they have no commonality and you are on your own for software. Looking at a more universal solution that could be open and commoditised, and become cheap like PCIe risers for GPU mining. ISA 3000, get the sucker on life support for the next millennium 🤣
Edit: So there's another end to the cable... as long as we standardise on the connector, we can do ISA peripherals with no edge connectors at all, new ISA cards becoming "chewing gum stick" boards or another card pack sized unit. Maybe have a conventional "loadout" of cards combined on single card, VGA, sound, SD storage and PS/2 port... ready to plug to adapter on original board, or to a new x86 mini board, or to modern or emu.. (Plus also if you had a card set on an 8 slot backplane it would be cake to switch one wire and be running it on 286 or pentium or whatever)
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.