FedEx Flat Rate Shipping

I have a client who ships through FedEx and wants to change their cart options to charge one of three flat rates for:

Ground Shipping (1-3 Days)
2-Day Air
Next Day Air

The products are perishable food items, and the three rate options would be the same for all products. I've tried an existing FedEx module and it seems to be designed mainly to give a quote based on variables like weight or number of products, which is not what they asked for (and it's acting buggy anyway). I looked at the other default modules like USPS and Table Rates (what they've been using up until now) and none of them look like they give me the ability to set up shipping this way either. I don't see a way in the Flat Rate module to set up three rates for the same zone. Am I missing something in one of the existing modules, or can anybody recommend a shipping module that would allow this type of setup?