I think a basic trading NPC is necessary along with the current classes in order to take advantage of a new leveling system. This NPC would replace the basic MC villager and would trade various goods for poke-bucks or other items. This would also ease MC players into pixelmon as this NPC is similar to a villager.
In conclusion, I think multiple NPCs would benefit from this system, as move-tutors and shop keepers now have additional mechanics in order to invest time in them. To fully take advantage of this system and to help ease new pixelmon players into the new system a basic trading npc similar to a villager would help ease the gap between vanilla and the mod, as well as supply many functions lost due to pixelmon systems.