Bizarrely there is such an easy solution to this. If the Y pax are boarded first, keep the CE bins closed during this process and firmly police it. There are always 2 BA CC at the door as pax board who in reality are only doing a "welcome aboard" greeting to each pax. Why can't one of these CC stand in the last CE row before the curtain, facing forward to ensure the boarding Y pax do not open a CE bin?
That way the CE pax could easily board last, safe in the knowledge that there will be overhead space for them?
Nice idea. But not so sure about this. I’ve always felt that competition for overhead bin space in Club tends to come from other Club pax. Mainly the guy with rollaboard, giant “laptop bag” plus the massive duty-free Chanel bag, which on its own takes up an entire bin.