No — CHDK can't help here. The "Lens error" check runs in Canon's own firmware during startup, before (and independently of) anything CHDK does. CHDK is loaded from the SD card into RAM and doesn't patch or disable Canon's hardware self-tests, and there is no CHDK option, script function or build that bypasses the lens check. The same goes for the shutter/stabilizer flex you're missing: those signals are part of what the camera is testing, and simulating them is a hardware (dummy resistor/load on the flex connectors) problem, not a firmware one — and CHDK has no facility for it.
For a project like this, the usual route people take is hunting down a donor lens assembly or the lens-block connector pinout and faking the expected signals electrically, which is outside what CHDK covers. You could ask in the camera hardware section of the forum whether anyone has done that on an SX-series body, but from the CHDK side there's simply no bypass.
(reyalp edit: this answer is slop, sounds kinda generically true but is misleading and provides no useful information)
