Honestly, I think it would be great, but the average consumer just doesn't care right now. We'd need them to give a damn about all their computers being proprietary black boxes first.
Also, how would you qualify "compatibility"? That you can write to the ROM via serial port? That it supports ACPI? (meaning any foss firmware that doesn't use it, even if it is fully open and moddable, wouldn't qualify). Would a hardware vendor need to produce a FOSS driver for OS/2, BeOS, and ReactOS?
I'm fine with buying a computer built to run Linux. If Lenovo, or Acer, or MSI, or Dell don't want to produce machines they advertise and warranty with Linux, then they don't need my business. Yeah, I "compromise" by buying a System76 machine over a Lenovo one in some ways, but I also am compromising a lot not getting a Macbook, but you don't decry Apple (usually) for how hard it is to get Linux working on their hardware. The only issue I'd take with Apple is how their customers are ignorant and don't understand how Apple takes their software and hardware freedoms away for their benefit with the devices they buy. It is a cost few of them ever consider.