Are there all in one external water pump solutions that can handle more than one 3090 at a time? This would be about 10 or so Aorus Waterface 3090s. Or is it a better idea to convert them back to fan+heatsink configuration?
Yes, there are, but you'll reduce your ROI substancially.
Also consider to buy watercooled backplates for the 3090 cards, those GDDR6X memories are really toasty.
Why? He has this cards with an installed watercooler, so how will this reduce the ROI?
Are there all in one external water pump solutions that can handle more than one 3090 at a time? This would be about 10 or so Aorus Waterface 3090s. Or is it a better idea to convert them back to fan+heatsink configuration?
By and Mora Radiator and a waterpump with expansion tank. I think this will work. I saw many other watercooled rigs.