That's a really good argument. Personally - and admittedly this is purely speculation - I think they would find some creative way to conform to the letter of the law without a drastic shift in business model. Someone elsewhere suggested, for example, something akin to an agency model, where they pay some amount to a sourcing company, and said company then retains a pool of workers that service requests from all rideshare and delivery apps. They could spin it into an opportunity to become said middle man themselves and profit from competitors and/or enter different gig economy verticals. Or they could settle for some middle ground with some loss of coverage but still more or less the same service. Or find some way to devour or partner with the taxi industry proper. Etc.
The thing w/ regulation and precedents is that it doesn't have to be Uber. If a precedent is set by any other company, your hypothetical scenario of risk to profitability profile would affect Uber regardless, so it doesn't seem in their best interest to just part ways with CA and call it a day.
On an opposing note, something else to consider is that the rest of the country (or the world, for that matter), may not agree with CA policymaking, especially as the CA political landscape drifts more and more towards the radical left side of the spectrum.
With that said, I have also read that Uber did do significant changes to its platform for the UK market (another place where there was an existential crisis for Uber). So platform changes are not entirely outside the realm of possibility.
This seems a bit misinformed. The reason they stated for leaving CA is due to logistics, i.e. a company can't process hiring paperwork for hundreds of thousands of people out of thin air. A more apt comparison would be your state government saying you have 6 months to rebuild your wooden house with bricks or face exorbitant fines. In that position, it wouldn't be a tantrum for you to decide to leave said state.
Regardless, CA is a big market for rideshare, so even if they leave, Uber will surely come back to CA once they make whatever changes they need to their platform to conform with the local regulations. That's what they did in Austin.