The simplest way to do this would be to create different shopper groups and the client can then just add 4 different prices to each product. It should be this easy for this client. These prices would be based on the vendor currency, but from your description above, that seems to be what's needed.
Behind the scenes, there's going to be a lot of changes needed
- IP lookup so that unregistered users get to see the right prices
- Use country in the billing address to determine which shopper group they get added to
- If the vendor currency changes depending on the shopper group, then more changes are required
- One additional approach would be to change the store url at the web server level (e.g. europe.mystore.com) and then check the URL within Virtuemart when displaying prices.
Best of luck,
--Rich