If you have a USB trackball and USB spinner, then an Opti-Pac is totally useless for you.
An Opti-Pac is designed to have devices direct wired into it.
If you wanted to direct wire your devices using an opti-pac, you'd have to convert them to non-usb devices, which would requre either swapping the optical encoder boards or modifying the existing boards (assuming that is possible).
This would definitely be a lot of work.