Hi Myles,
I only just found the time to look into this. Turns out it is possible to add the necessary fields for an address fields in MailChimp without any changes to the plugin, although I will work on a way to make it a little easier.
Right now, you can include the following HTML in your form mark-up to render the address fields.
<p>
<label>Street Address:</label>
<input type="text" name="ADDRESS[addr1]" placeholder="Your address">
</p>
<p>
<label>City</label>
<input type="text" name="ADDRESS[city]" placeholder="Your city">
</p>
<p>
<label>State</label>
<input type="text" name="ADDRESS[state]" placeholder="Your state">
</p>
<p>
<label>ZIP Code:</label>
<input type="text" name="ADDRESS[zip]" placeholder="Your ZIP">
</p>
<p>
<label>Country:</label>
<input type="text" name="ADDRESS[country]" placeholder="Your Country">
</p>
In this example, ADDRESS is the name of the list field in MailChimp.
The country has to be a two-lettered locale like US or NL. If you omit the country field in the form your default MailChimp country will be set.
Not sure how familiar you are with HTML but you can of course add more attributes or change the field types, for example to show a select box for the country.
Hope that pushes you off in the right direction. I will think of a way to include address fields in the “Add MailChimp field” tool so you can use that to generate the form HTML for you.
