Something that has disappointed me with Team Rocket in recent sagas, especially in Journeys, they haven't really caught a lot of pokemon.
One thing I'd love in Journeys, if for James and Jessie to return to Arbok and Weezeing and reclaim them. It is their signature pokemon and I feel like they should finally get them back. I think the other pokemon by now can handle themselves. Maybe even visit Cacnea and Mime Jr. again.
As for pokemon I think they should catch, I think Nickit is a 100% Team Rocket Pokemon and feel like it would be the perfect pokemon for Jessie since James has already caught a Morpeko.
Sadly with Journeys likely coming to an end this year if rumors of Gen 9 are to be believed, I don't think they will catch anymore pokemon. At least not ones that would make a massive impact on the show.