I like the idea. Although I wish they implement NPC opponents too. I don't wish to battle overtrained pokemons against pro players. Instead I would love to play with my friend dueling NPCs where skill and EV training isn't all that important(but still to a certain degree).
Would love to train this way too, would really be a welcoming feature for sure. Ofcourse this would require duel tag npc players on map just like in newer generation games.