Marketpress: Group stores/products by geographic region?

I am setting up a virtual Marketplace/Mall using WP MU and Marketpress for a small country where the geographic location matters.

Users will want to filter the available stores or maybe products in the mall by geographical location. For exmaple, show me just stores/products available in regain A, B or C.

If the marketplace was for the USA, users could maybe list stores or products by state rather than see stores in other areas that might not be relevant to them.

There are no real addresses in my country so things are not usually shipped so easily like in other countries.

Ideally, the way I see people using the system would be selecting from a drop down list on the mall home page to show just one particular region, town or area. Listing stores or products in that particular region which they could jump to.

...or many integrate this at least in an advanced search.

Is such functionality possible with a plugin? If not, can you suggest the best way to hack the code to do such?