"risk of killing sd card"
100,000 read/write cycles is the normal lifespan for flash memory, cmon now. That includes the internal NAND which is also eMMC flash.
You will run out of room on said sd card far faster than you have to worry about its wear and tear.
If you choose to not buy extra cards for your games (b/c it's expensive and inconvenient), you'll be stuck with erase/redownload from the internet style data management. And yes, that brings you back to your alleged problem with wear and tear.
Why not just buy a 4TB hard drive and not have to deal with that?
And for those making the "security" defense for Nintendo, that's absurd. A compromised system can load pirated content from any media format, as the title of this article suggests. An unhacked system should conversely be able to load data from any format without issues because the data is protected by digital signatures and encryption. It's not the archive format that determines security, it's the OS's code being up to snuff. The HDD itself as a format doesn't change anything.