Adding form types is not for beginners and should only be done if you know what you're doing.  To add a new form type, here are some hints on how to do it and how to contribute your form type:

1) Create a new type that extends AbstractFormType and implement it as you want

2) Obtain theprocess engine configuration and tweak it as described in step 3

3) Do processEngineConfiguration.getFormTypes().add(new MyCustomFormType())

To contribute, send in a signed contributor agreement and submit the formtype and a test case attached to a new jira issue.