One of our Swedish customers calls it soft repowering. That means keep as much of the existing installation as possible and keep investment relatively low.

This soft repowering we have done for one project in Sweden. Leaving the foundation and tower in place of the existing Führländer and replace the nacelle, rotor and controls with a Vestas V90.
An adapter is engineered to have another brand of nacelle on top of the tower. Of course all important calculations are made to assure it is a safe and reliable solution.