Yes, it should work: An m-ITX with 6 SATA ports and a 2P SATA controller like HighPoint Rocket 620
(low profile and works with Linux) gives enough ports, and there's room in the PC-Q08 for the drives.
Cooling: With the CPU cooler at 1300 rpm, stock case fans at half speed with Zalman Fanmate and 100% load 24/7, CPU temps hover around 70 C and HDD temps around 40-45 C - borderline, but still OK.
Cooling should be OK even with another two drives if you turn up the fans or reduce the load. You might consider replacing the stock fans (especially the 120mm top fan) if you want it quiet as well.
Nice build, probably going to be similar to when I'm done with mine
I've always had my HDD's around 33-38C or so, and that's what I prefer. I find myself really uncomfortable once they go above 40C, so that's an issue already right there. Also I'd figure having a really cramped and stuffed box just makes temperatures that much worse, especially when you're trying to keep a machine close to silent as we do. So no, while theoretically you could use 8 sata in a PC-Q08, I disagree it makes any practical sense from a silence and cooling aspect. I'm sticking to probably 1 optical, 1 ssd, and 4 data drives in my case, which I think is about the same as you. Anyways maybe I'm just more picky about cooling and temperatures, but I always have been, that's why I'd never make a fanless system too.