Multi-person application forms

There are many use cases in the real world where multiple applicant details are required in a single submission. For example, opening a bank account, applying for a mortgage or loan, booking flights or holidays, and applying for housing.

In each of these cases, the application is a single one but certain information within that application has to be repeated for each person applying. This is perhaps most common when opening a bank account in joint names.

I need to create this functionality in a similar way for a site we're building in Drupal and plan to create a new module that hooks into webform to do it. Before I start, I'd appreciate any pointers or suggestions, or would like to hear from anyone who may have attempted something similar in the past.

I'd also be interested to know if anyone would be interested in getting paid to develop this module. I've posted that separately on the marketplace: http://drupal.org/node/1396142