the URL works within communities already (replacing "trending" with "promoted"

Yep, and it also works with "my" to see all promoted posts in the communities that you're subscribed to, i.e. https://steemit.com/promoted/my (except that it seemingly doesn't work from Upvu because they rewrite the URL, and don't seem to have a promoted page).

It would definitely get more traffic if one of the sc accounts (could be one of sc04-sc08 (@o1eh 😉)) started visiting more frequently

Agreed. sc01 used to watch it, but I think they were focusing on just the top-2 on the page, and they seemed to lose interest when the typical promo amounts dropped below 1 SBD.

Although it would be better than a bid-bot. Hopefully you understand what I'm getting at!

I think I do. At least the payments are being distributed to all investors that way...