Okay, finally got some time to play with my DCS-7060CX-32S-R further. Here are the findings so far:
1. There is no SATA / SATA DOM header on the motherboard. However there is /mnt/flash. So I guess it must be some kind of soldered on ROM chips that won't be replaceable easily if they are worn out.
2. So the only way to get extra storage is via the M.2 (SATA) - the device will appear as /dev/sda. However, looks like ABoot is expecting the filesystem on /dev/sda to be FAT. And, EOS is expecting /dev/sda to be ext4. Therefore, I cannot pre-extract the .swi to /dev/sda since it needs ext4 I believe and ABoot won't see the files if it is ext4. However, I can place the .swi to /dev/sda so it boots off it quite a bit faster. EOS can still see files on /dev/sda even if it is fat (and complains about that tho).
FYI the memory I am using are 2x Micron 8GB 2RX8 PC3-14900E (UDIMM ECC).
I have decided to go a bit adventurous so instead of using M.2 SATA drives, I have purchased an adapter (a Sintech ST-NGFF1ST) so I can use an old Intel X25-E SLC SSD lying around. I need to be a bit creative about how to secure it in the chassis