That would require making your own GPU PCB, and maybe a year's worth of studying on electronics and power supply design.
A year’s worth of power supply design? Have you looked at the LM7805 datasheet? The circuit is one regulator and two capacitors...
And designing a 250W-capable linear regulator is not as simple as just hooking up a LM7805.
So with a modern CPU and GPU, your talking ~400W of power to the actual components, and nearly 500W wasted in the linear regulators. This of course also means you have to get a 1000W PSU as a bare minimum.
Yeah and good luck driving a 200W linear element (if it even exists, lol) with a few op amps--the driver which should deliver a few amps into the gate/base of the pass element, which in and of itself is a pretty difficult challenge.
LMFAO you can't be any more wrong. You need /much/ more careful design to get GPU-compliant performance. The dI/dt on modern ASICs are insane, and you need an insane regulator to deal with it.