Efficient workflow for web ads multiple sizes

I've been working with a master illustrator file with many art boards, but I also have this problem. The only time-saving thing I've been able to do is find the ones with the same proportions, but it only bring the versions down from 10 to 6.

The other method I was considering was to build them in InDesign and use the "automatic layout adjust" - but that would only save time if I needed many variations of the same 10. If I'm just creating one new batch of ads, it doesn't help. If anyone has a better solution yet, I'd love to hear it!

Indesign and data merge is an option I use for situations similar to the example you linked.

I would think with all the different web devices around these days and the various display sizes  and resolutions you would need many different layout and content to be approbate for the different device displays. Its not just a matter of scaling you need your multiple layout and the content will vary between them as will the banners.   If I were you I would use google searches to see what I could find that may be helpful for what you want to do.  You know what you would like to do your best qualified to do the searching.  Consulting a professionl web design consultant may be the best starting place.  Help you know what to search for.

If the sizes of the layouts are proportional you can export from Photoshop to the different sizes. If the proportion of the sizes are different one option is work with linked files: Work with Smart Objects in Photoshop