Can someone like... boot Windows 98 on these on a system with no ram?!
Conceptually - yes, easily.
But to do it literally - I'm not a low-level motherboard EE, but I'd bet you're looking at 5 to 7 figures (US $) of engineering work, to get around all the ways in which that would violate assumptions baked into the designs of the CPU, support chips, firmwares, etc.
Theoretically anything is possible with enough thought and work.