So it's pretty easy to make new Pokemon, but I think it's getting harder for Game Freak to come up with new, useful moves.
Let's come up with some interesting ideas for them.

I was thinking about how Roar isn't useful on the opponent's last mon, and while it's great for forcing out stat boosters, the forced switch can be disadvantageous at times for the user - e.g. if you want the opponent's current mon to stay in and they'd rather switch, they can get an attack in and get you to switch them out at the same time.

Meteor Mash (Name pending)
Power: --
Throws one opponent into entry hazards. Flying-types and levitators make contact with Spikes and Toxic Spikes.

This is great for its reliability if you have lots of hazards, and it can absolutely destroy things like Tornadus if you catch them switching in (25% SR damage, 25% SR damage, 25% spikes damage, poison) but it has the downside of not removing stat boosts/substitute/working through Protect/Taunt. It's useful against the last mon, and it allows you to set up T-Spikes and then poison the thing currently switched in.