The inability to transfer to a BA HHA is also annoying me. My daughter is in a HHA with her grandparents. To get access to her grandparents BMI miles (the 1k sign-up bonus which I cannot move inside a BMI family account), I would need to break up the HHA and thus close my daughters BA account. Too much trouble for 2k miles.
But I genuinely don't see what the problem is, since inside a BA family account everyone can still see their own pot. It is not like avios.com HHA's where the miles were genuinely pooled.