Ball pickup doesn't always have to be about, well, picking up balls. Here's how I have worked in some additional ball striking opportunities into our ball pickup.
Send your players to whichever side of the court has the most balls on the ground. Coach is on the opposite end of court picking up. Have the players send the balls to you with one or more of the following challenges.
Serving - Have them serve into the cross court service box from the baseline.
Topspin forehand - bounce feed and send across the net with as much topspin as they can muster.
Backhand - bounce feed, then work on backhand style of their choice - one hand, two hands, slice.
Lob - bounce feed and aim for behind service line, middle of court. Add some topspin if you are able.
Sometimes my students aren't crazy about ball pickup, but they will wear themselves out with these simple challenges, even scrounging for additional balls to hit once they have exhausted the supply on their side.