You go buy a real desk, and a real drafting table for the drawing work, because you don't have to build anything you can hit the ground running in a day or two. Then modify if needed, and make the computer hutch and shelves above it.
A corner table setup for the Wacom and keyboard drawers and multiple CPU's and monitors you whack together with square tube or that Erector style industrial framing, and since you do get Earthquakes you bolt the shelving straight to the studs.
Lots of room in the corners underneath for CPU's, UPS's and Computer Shite. Install a light so you don't kill yourself crawling around.
Install a gate if critters like to crawl around down there and knock plugs loose, shed all over the cooling vents, and chew or pee on things...