Benefits of using a base theme?
If you're not doing a traditional 3 column with header and footer site layout, then no - you probably won't get much out of something like Zen.

That said, you can still leverage the awesome Zen Grids gem with SASS and get the benefits Zen's grid system without any of the cruft from the base theme.

Anyone who has themed enough Drupal sites understands that you're going to be dealing with machine-generated HTML at some point (either from Views, or some other contrib module). You could spend a ton of time overriding all the theme functions to get the exact HTML you need so you can apply the col-xx classes your grid system of choice needs, or you can use the classes that already exist on the pre-existing markup and make them compatible with your grid with Zen Grid's mixins.

I like to say that Zen Grids acknowledges the reality of Drupal theming and comes up with a system that works with Drupal as opposed to against it.