I find that SOS battles can be a good addition to wild Pokemon battles. And are useful for EV training and finding wild-held items. I plan to rework the Macho Brace to give +1 IVs to a Pokemon after defeating a Pokemon for my project's needs, so that rework highly benefits from this add-on to the Deluxe Battle Kit.
The expansion of allowing Pokemon trainers to be called into an SOS battle is also great. There are a lot of possibilities that are enabled by allowing trainers to be summoned into a battle via an SOS call. I still have yet to be thorough in testing how this plugin works alongside the Dynamax, Tera, Z-Moves, and the Deluxe Battle Kit itself. I have yet to encounter crashing or bug issues caused by the SOS add-on itself.