Successfully installed OpenWRT on Bullet 2HP router, configured it to access existing local network broadcasting from separate device as well as broadcast Bullet's own secondary network without an ethernet internet connection. Additionally configured an old Linksys WRT54Gc (compact) to act as a switch, used ethernet port from Bullet 2HP router's Power-Over-Ethernet injector to provide internet access to ethernet-connected devices on the Linksys WRT54Gc.
All of it works fine so far, but there are definitely performance hits at each step. Thinking ways to improve are: