They could have removed the shield sharing rule, allowing people to freely mass turrets. (makes Mas turrets too good without a drawback)
They could have allowed the firing player to place extra blast markers touching the ships that are massing turrets (representing their shields going down) but where all blast markers are placed on a direct stem-to-stem line. (you will have 3 blast markers all around 3 ships which starts to look like ur example)
Or they could have just let the situation slide and said "hey, if you don't like them being so beardy don't bunch your ships up". (yeah they could just not allow mass turret at all)
What they did is actually chose the simplest solution that affects many gaming areas systematically. Apparently they forgot to clarify it entirely for every situation (where to apply it, or where to take into account the physical touching of the BM)
Simpler gameplay = faster gameplay = less possible arguments = more fun = easy to understand ,apply and use. I really hope HA just keeps the old BM thing (as per armada)