Clone a shipping module or define a new shipping attribute under table rate module?

For a site I am working on, we are using the table rate (using weight) as the preferred shipping module. The actual mode of shipping is by airmail and the rates are as defined by our local post office.

We want to also provide users the option to have packages couriered (something like FedEx) to them. This will likely use the table rate of the courier company (different from the govt. run postal service rates).

At this moment, we are unsure whether we need to clone the existing table rate module and use that to define the rates of the courier company or whether to define international courier (with its own set of table rates) as an additional attribute to the existing table rate shipping module.

The second option sounds like the wrong way of going about it, but I will be very thankful for a confirmation from experienced Zenners.

Thanks in advance.