CX gives lounge access to their Silvers OW Ruby equivalent, but their lounge offering is usually much larger than BA’s and the benefit does not extend to other OW Ruby’s.
I would allow Bronze to use avios to get into the lounge, it would be also a financially sound option for BA so they can polverise Avios wallets of clients that hardly accrue enough to spend on flights, leaving many small wallets with unused avios which put pressure on the balance sheet until they expire.