That would be a great option if Tesla offered the part (or you could otherwise source one), rather than replacing the entire MCU, as Tesla does. The real trick is getting the critical car-unique data (encryption keys to tie back to the mother ship, hardware configuration files, boot partitions, etc...). Tesla service has all of that info and reprovisions the new MCU with the correct data tied to your car VIN that you need.
The rest of us just attempting to repair need to get that data, and Tesla won't release it to an end-customer. So if your MCU is toasted enough to not boot, the only way to attempt to extract that data is to de-solder the chip to try and read it. Once you do that, you might just as well repair the daughter-card you already own.
If you are doing this proactively before the eMMC dies, there are ways to extract the data you need without de-soldering, and you could get a working MCU or card from a salvage car (they aren't standard Nvidia boards you can buy from them) to write that data to. However that's more complicated, in that in addition to the Linux partitions on the card, there's a separate "gateway" processor/storage that you'd also need to configure, and that's a bit trickier.
All in all, the easiest/least-expensive route is typically:
1 - Extract your data proactively, while the eMMC is still healthy
2 - Write to new high-quality chip
3 - Swap chips on the daughter card you already own.
There is some small risk in damaging your daughtercard during the soldering steps, so you can wait until it actually fails if you want, but then you need to regularly do step #1 in order to makes sure you have the current data (keys, boot partitions, etc...)