I added a remote to my SP lite and made it so I can stop the motors to save power and can also start/stop ball feed. The remote is important, no doubt about it because you need to take breaks and it's a real hassle going back to the machine every time you need a pause for whatever reason, including the start of a session.
2 line, only important if you have a partner.
Various depths, only important if you want the convenience of pushing a button to change the type of shot to work on. I just work on the same depth of shot near the baseline and then set the machine up manually for another type. But I don't practice every type of shot because I'll hit around with a partner too.