Conditional Signatories in Workflows

I have a form that will have between 3-6 signatories.

• Signatory 1 - Always needed.
• Signatory 2 - May or may not be needed. There is a checkbox on the form to indicate whether that signatory is needed.
• Signatory 3 - May or may not be needed. There is a checkbox on the form to indicate whether that signatory is needed.
• Signatory 4 - Varies, but within a fixed pool of 3 people (division heads).
• Signatory 5 - Always needed.
• Signatory 6 - Always needed.

Additionally, each of these people will need to select a radio button and some of them may provide comments into the form.

I am Signatory 1 and when everyone else signs, it will come back to me for processing.

What's the best way to approach this using Workflow for Signatories 2-4? Would I edit the workflow each time to add/remove Signatories 2-3 and customize Signatory 4? What happens if the workflow changes while a document is still being routed?