The phrase "extensive redesign" means making significant changes or modifications to something, typically to improve its overall design or functionality. Full definition
The popular midsize sedan is just barely removed from a pretty extensive redesign, however, more than few changes have been made for the newly available version. (drivespitzerkia.com)
This is notable because of how extensive that redesign was at the time. (corvettedreamer.com)
Acura's RDX, the top - selling luxury compact crossover in the U.S. as recently as 2015, is undergoing its most extensive redesign in more than a decade as it squares off against a wave of new rivals. (autonews.com)