Developers have commented here
I have to fundamentally disagree with you. Currently lockering stuff isn't a decision, it's a chore that takes away from the fun and spontaneity of the game. I do not have the Rock Heart in my locker, which means one way or another I need to do some scumming to play a Transmuter to his full potential... and as a result I rarely play Transmuter. No matter how well you balance the items, there will always be reliable standby choices that will populate the majority of people's lockers, and this limits your ability to try a different approach on a whim.
Now, I do agree that there will never be enough locker space to satisfy us, which is my suggestion is for the space to get exponentially more expensive. Let's say 10k GP for the 7th slot, 20k for the 8th, 40k for the 9th, 80k for the 10th... even I would only have 9 locker slots currently. This would add a gold sink for the inordinate amounts of cash some of us are bringing in, while also granting that wish for extra locker space.