1999 Passat 1.8 abs problems

You're talking about getting the control unit (not the hydraulic part - just the electronics) fixed, yes?
Nothing to "bypass" - simply unbolt the control module from the hydraulic unit, and send it out.
Car can be driven (albeit without ABS, traction control, etc.)
Cover the electrical connector with a plastic bag to prevent water ingress.

In my experience, the absolutely easiest way to get the ABS module out is to first remove the driver's side front wheel. Next, remove enough of the wheel liner screws so the liner can be flexed enough to reveal the back of the ABS unit, where otherwise hard to reach fasteners are accessible.