Point of being part of a club is so you can train on a regular basis, have proper judgement on what you are doing from a different perspective besides your own, and have proper help, both decoy and group.
Some clubs tend to lean more towards more common breeds but a good club will welcome any dog with proper obedience, temperment and defense/prey balance. A dog that does schutzhund has to be a fine balance, and the experienced trainer should assess all of that before allowing the dog to start the sport.
In addition, a dog that YOU are handling the dog wont go to its full potential, also being behind the sleeve isnt for everybody if it is done improperly theres alot that can go wrong, not only to the decoy but the dog too, another thing that confuses me is how you could do a send out, escape, or an escort drill solo