See the comments here: Create a new type of connector
Looks like a delegate is just as good. And less code to write.
What I have also done in a few cases is write a small script lib in js or groovy/java. So you can then configure your commends with a dsl in very basic code of a script task. Have found that it makes lives much easier to copy and paste usage between BPMNs and from documentation. You can also easily plug it into a ide for code completion and get all the type checking