I'm just digging into the MailChimp module and trying to configure it best for my use case.

Since we have a decent number of fields in Mailchimp (and since some of those are not public) it would be helpful to be able to choose which fields are available on the signup form.

I could see this happening in one of two ways in the list edit page MailChimp List Settings > Merge Fields fieldset - either 1) Checkboxes next to each field for either including or not including the field on the form, or 2) Adding an additional option within each field's mapping drop-down select options for "Do not show".

I may be missing some important detail here that would make this feature unnecessary, but if I'm not, I see this as being useful.