If you're going to use pole brackets on piers, you could run a trencher around the perimeter and tie them all together. Would probably need to go to frost depth to prevent uplift. I have heard this type of foundation called a "rat wall".
Did something similar on a smallish shed, but only went down about 2 feet. Piers were augured to full depth (4' here). Connected it all with rebar, then poured. Set anchors for metal uprights with a jig. Hasn't been thrown out of the ground by frost yet, but it's only been up a handful of years so far...and I'm not living in it.
Did something similar on a smallish shed, but only went down about 2 feet. Piers were augured to full depth (4' here). Connected it all with rebar, then poured. Set anchors for metal uprights with a jig. Hasn't been thrown out of the ground by frost yet, but it's only been up a handful of years so far...and I'm not living in it.