This is exactly the problem. Look at the global semiconductor industry right now. AMD came out with new processors recently. NVidia came out with new graphics cards. Both companies have released the products in the thousands where consumer demand is hundreds of thousands of users. They simply can't manufacture semiconductors fast enough with the given state of the world.
And these older products may no longer be produced, or they're making something that's somewhat like the original product but has different timing or voltage characteristics because they took some design and moved it to another fab. At the very low or high end of the volume production this isn't a big deal, but 200,000 units is actually below the
threshold for nvidia to really work super hard to accommodate you. And the problem isn't just (or even *mostly* the CPU; if there are any other custom ASICs on the board you'll need those fabbed as well, and ideally the new ones will be identical to the old ones in every way, which is not trivial)
This isn't like making bolts or airbags; IC's need extremely expensive fabs to be made and those fabrication plants are constantly in flux. The fabs make ICs of a particular sort (voltages and timings are dictated by the feature size of the fab) and there just aren't that many fabs out there with spare capacity.
If I had the task of rolling through 1000 repairs a month, I'd gamble on being able to do it with refurbishing existing units. If tesla was actually throwing these out in the early phases of this issue, it indicates they didn't understand their liability about this whole process. Those cores are pretty valuable.
If I had the task of rolling through 30,000 repairs a month and had a hard deadline to finish, I'd tell mgmt they're better off making the existing MCU2 talk to an analog tuner / remote instrument cluster and put a feature flag that disables "mcu2" features.
I'd also have hard supply contracts lined up with whoever can make all the BOM for the MCU1 as the alternative.
It is solvable, but it is not good.