Yeah those are what I'm looking at, but even then we've been at 8Gb for years. Manufacturers only want SLC NAND in these for valid reasons and I guess the market isn't pushing for now. The 9x8 is useful but the 3.3v that eMMC wants means I can't power off a single cell li-ion without a boost. It's all a nightmare. Trust me I've looked for solutions, unless you know of any silver bullets that came out recently.

And as you surely know, I usually can't boot from NAND (due to the aforementioned annoyance) so I'd have a boot flash and a storage flash and that's unideal.

I'll note though that the controllers are small. You can RE the die size of a common eMMC<->NAND controller and it's much smaller than 9x8. I won't share which because I honestly don't remember if we got an NDA in place but considering they all stack dies in there anyway, I don't really see that as the size driver.

A lot of MCUs can boot from XIP QSPI/OSPI NAND. quite a feat of compatibility engineering - they made the NAND page size match QSPI transfer sizes commonly used to populate caches, so instead of bit level reads, the flash supports only cacheline level reads, which is usually what you need for XIP anyway.