I see your point but,
- BC had a hard life steaming fast in war time so lots of hard use
- its your only 13.5 ship so cost will be higher to keep in inventory
- the USN got away with using CAs till they got new fast BBs
- if you are lacking ships with speed will the KGVs not be built faster to fill in ?
I would just put up with 27Kn escorts its not to slow till you get the KVGs, I'm just not sure its worth wasting one of the precious rebuilds on a ships that will never be able to stand in the battle line due to guns and belt ( much better to do the rebuild on a Barfleur/Majestic and get a 1st class fast battleship,but you never know what ships would be in line for a routine dock when you have the cash/time to rebuild
so might happen)