I really wish that BA would increase the size of the personal bag to easyJet dimensions which fits under the seat and make this one bag the free allowance. Like easyJet they could charge extra for a second larger cabin bag, and maybe allow this free with Gold/Silver/Bronze.
The cabin bag problem is only a problem on flights with a large percentage of people flying on HBO-only tickets. And part of the USP for these tickets is that you get a proper full-size cabin bag included in your fare, unlike on the LCCs.
I like Aer Lingus' solution, where you have to pay to take the cabin bag into the cabin but you can check it in for free at the check in desks. Avoiding having to lug my bag through airport security and being able to take full-size liquid toiletries with me is enough to tempt me into checking in the cabin bag for free, but it wouldn't be enough to tempt me to pay £50 for a 23kg hold bag. I reckon it will be for a lot of people. After all, I'm really only choosing the HBO fare in the first place because I resent being absolutely rinsed on hold baggage fees.
Interestingly EasyJet have also cottoned on to the fact that the hold is the best place for luggage and now you'll find that the cost of a 15kg hold bag is basically the same as the cost of a large cabin bag.