Maybe it needs some more testing and fine tuning, but so far I think I like the battle rating limit because it matches the difference in time acceleration between open world and battle instance.
The attacker has to sail in a fleet now. Not just a small fast ship that forces the enemy into the slower time acceleration of the battle instance by attacking to make it possible for the larger ships to catch up from far away in the faster time accelerated open world and then jump in.
Also all battles I had with a higher BR difference on any side where boring for me, as there was no challenge at all. This change reduces the number of unfun PvP battles that I anyways don't want to participate in and increases the number of fun PvP battles in my opinion.