Changing SQL Server authenication

We have a database which has always SQL authenication and has 300-400 named users. Upgrades to the database have always been done as ‘sa’.

There is a new upgrade required. The new owners of the software now want use to change the authenication to Windows NT to complete the upgrade. They suggest changing the authenication to Windows to complete the upgrade then back again to SQL afterwards.

Can anyone see any difficulties with this? Has anyone got any advice on this?