They are running or planning to run just about every variation of system. From high buck cat back stainless steel systems to forty dollar add on aftermarket mufflers like rumble or thrush.
The harsh truth about the basic fiesta is that it is locked down in terms of what we can do to the engine. It is very limited.
The upside is that leaves plenty on the table for other things like cargo management and appearance upgrades.
Which, ironically, is where Ford marketing efforts fell so catastrophically short when the Fiesta was reintroduced to the American market.