Thank you all for your messages
Concerning the modifications, I have changed the following interiors parts :
_ST150 door handles
_Alluminium gear lever knob
_Gear lever synthetic leather gaiter
_3.5mm jack plug to MP3 devices
Exterior plastic moulding are ordered to have a full Panther Black ("Noire Scala" in French^^)
And to finish, I would like to install a Mongoose Exhaust to change the Fiesta sound (Milltek has become too common for me), I've never heard a Zetec S with Mongoose Exhaust but I think the rendered would be fun.
Picture with a friend to conclude :