I just read through the whole thread. I think the opinions expressed previously still stand. However, I want to expand my previous answer.
Option 1 is to get an upper and a mag-well converter to use an existing AR lower. This works fine.
Option 2 is to get a dedicated lower. I have built a few of these now and recommend getting a glock mag pattern lower for simplicity, chosen for the roll stamp you prefer, and going for a Sharps Bros dedicated lower if you want to go all-in on a different look. I have a handful of the Sharps Bros lowers just because they are different.

Side note, I built a side-charging upper for a .45ACP build a few years back and think that's a good way to go for a PCC. Like the Sharps Bros lowers, I built one just because it was different. All AR pattern rifles look the same, so something different was appealing to me.