Is there a way to save all scene objects as an incremental version, rather than doing one at a time?
That's what the manual and auto save functions of LightWave do. There's no need for extra plugins. However, should any of us have an older LW release, there are 20+ years of free plugins that help with saving (see Mike Green, Chris Peterson, TrueArt, etc)....but wanted to keep the previous versions, just in case.
...Wondered whether there was a plugin which could save all objects at the next version, rather than just one object.
I have something similar to this natively on Mac, time machine backs up every hour....I use DSynchronize to automatically backup a project folder to a different drive while working as well as saving an automatic backup of the previous saved version. It maintains an infinite number of versions of each file in the project folder. Filters can be set up to control the behaviour (not all files should be tracked, for example).
DSynchronize works either on command by clicking the "Synchronize" button, or works real-time and no user-intervention is required. In the latter case it will keep update the backup and adding new versions whenever the user saves/changes a file in a project folder.