Another difficulty playing tracker organs is mechanical stop action. Every stop has to be pulled and pushed by hand and sometimes it's not very easy thing to do (especially when you have to change several stops at a time).
Wouldn't it be great if an organ could preserve mechanical key action but add an electric (or solid state) stop action where you could also have thumb pistons, toe studs and multiple memory levels?
As a matter of fact, plenty of modern organ builders choose to build such instruments. It can be technically easily achievable.
My organ at Vilnius University St. John's church where I work doesn't have stop combination action. Every stop has to be changed by hand. The stop handles are fairly large and it's a heavy job for an organist to change registration. In this case, I often advise organists who play here to choose the repertoire wisely. Some pieces need even two assistants changing stops on either side of the console.
Do I wish that this instrument had a stop combination action? Not at all. I love it just the way it is and think deeply about what kind of music can be best performed here (keeping this in mind, there are far more choices than it is evident at first).
But if you happen to play a tracker organ with stop combination action, your registration choices can be (almost) unlimited.