If you want real quick change (hex keys only), and not action wrench/prefit setups, you are looking at Barrett, AI, Blaser, and a few others, most of which seem to start at 4k+ or so for a rifle, and 1k or so for a barrel.
I’d say with being QD and prefit, (by prefit I’m assuming ones people keep on the shelf, not that are capable, but you’ll wait 6 months for) your options:
AI AT-X/AT/AX
Curtis valor
Terminus zeus
If short action magnums are important, the either no AI, or you’ll have to get an long action AXMC or AXSR.
Everything else is going to involve kits or machining in something like a WTO switchlug.
You could also just take a viper barrel vice and bolt to a plate that fits in the trailer hitch if you have a truck. Then it’s just 2min to pop a barrel off and on. Keeping them at 75 ft/lbs or even 100, since they won’t be sitting and have never seez or similar, it won’t take hardly any effort to break them loose.
But the above three will be the easiest. There’s less prefits for the AI, though I expect that to change with the X.
Am leaning towards a Terminus for affordability and pre fit support. The AT-X close second.