For what it's worth, I have just emailed customer service negative feedback. Since the announcement, I have booked 3 flights on other airlines.
I don't have a long history with AY, having only moved to Finland recently, but I was OWE/S for a long time, and was on my road to jumping over to Finnair (Slowly, by selecting which flights I use my BA status and which I claim AY points).

I am giving up moving over to AY. Yes, I am just one small data point, but I am now physically unable to fly AY. I can't travel with carry on luggage only for a 2 day work trip. It is going to be impossible in winter, and very challenging in summer. Between my laptop, bag, and chargers I am already over half my allowance. I do need clothes and toiletries.

I did a test, and for a 2 day trip my luggage came to 9.8kg. I could not go lower. I am not going to wait 30 minutes at the airport for a checked in bag (ignoring the cost) when other options allow me to bring my luggage in the cabin with no stress.

Yes, the 8kg limit has been around for ages but it was never enforced.I fully support enforcing volume but not weight. It was getting ridiculous when people had guitars in overhead bins taking up the entire thing. As for the AY+ benefit changes, well that to me is of lower importance but a bitter taste none the less. I rarely needed to use my free checked bag, or took sport equipment. But of course it is a frustration for others.