Driver names are stored in the veh files for each driver (gamedata\vehicles\*series*\*team*\*driver*.veh). You'll want to edit these lines:
Driver="Emerson Peres"
Description="Form_Reiza: Emerson Peres #22"
Replacing
just the name. You need to retain the Form_Reiza: part in the description line though.
If you rename a driver in the veh file you'll then have to rename the talent files too (or at least the name contained within the *.rcd) so the drivers still have differing performance.
This will very likely cause online mismatches though, so make backups before you go changing anything