If you have a static list of approvers, you can hard code them into the form in a number of ways. I wouldn't think you'd need to use a people picker at all. For example, if you are emailing this form to approver 1, then approver 2 and so on, you could hardcode this in workflow in SharePoint Designer, or you could have a "To" field in your form (not showing on the form, if you prefer) that you can set via submit rules to you first, then the second approver once you've approved and so forth. If you can tell me more about how you intend the form to be used, I can help you with a sample. :)
Hilary Stoupa
