This was the missing piece of information (I didn’t pay close attention to anything around S922 the last months). Yep, with mainline u-boot PCIe/NVMe support might work and a bootloader in SPI NOR flash can run an OS directly from USB or NVMe storage.
For me personally the most important information around VIM3 launch is Gouwa’s NVMe test since this confirms that PCIe on S922X is usable. Unfortunately Khadas only focuses on fancy and cool looking stuff with full feature set resulting in high prices. But for me as a ‘use case first’ person with NAS and server use cases in mind a VIMS (S for server or NAS) would be the greatest device in 2019.
Simply remove everything not needed, add an ASM1061 for two SATA ports (and plan a Pro variant with an Marvell 88SE9215 for four SATA ports), combine this with a stackable enclosure allowing for efficient passive cooling (see ODROID HC2), 12V input and done. The OpenMediaVault HC2 image gets installed +200 times a week so if Khadas would manage to provide this at a competitive price (same as or below HC2) and manages to keep full compatibility with VIM3 and allows for a stackable design supporting 2-4 3.5" SATA disks then this would really sell well (if Khadas is faster than Hardkernel here).
IMO the best use of the single PCIe lane on S922 with the specific highly energy efficient NAS and server use cases in mind.