Right up my alley!
Here's a couple of workouts I would do with my mare when we were really conditioning.
If you have access to cavalettis and gymnastics, have fun moving your jumps around so you approach and leave at different angles. This will help your horses flexibility.
Throw a couple of poles on the ground around your turn so when you come around the turn your horse keeps his balance, keeps the consistant rhythm and has something to focus on. The more they have to do, the more you both will advance together.
Also, work on using specific commands. I.e., one ride only use confident, clear body commands. Another day, use verbal speech to transition your horse. The more you associate communication with each other, the stronger the bond, and the better you will perform!
I loved trotting circles over elevated poles. It's not easy when you have them set up for specific strides. This was always fun for me, kept us changing direction and planning what to do next.
That's the best part of forums, little bit of everything from everyone :)