Custom forms development questions for workflow

Sorry to have so many questions on behalf of our programmers, but its important that I can communicate what's possible to them.

1.  the GE Workflow forms activities do not have all the cool widgets or the data binding our programmers think they need (not sure what those are).  Could they develop their own forms using all the fancy widgets available in visual studio and wrap that with some code that would make it acceptable to use in GE workflow designer.  I think they could as long as the workflow has an input variables and output variables, but I need a professional opinion here. 

2. if we build our own forms, how hard would it be to integrate the custom code with existing workflow activities?

Jeff