My suggestion would be to look into resizing on demand, I suggest this library: https://github.com/derdesign/mr-image-resizeI have also written a small WP plugin that hooks into default image resizing that WordPress does, that also generates images only when needed, and not on upload (add_image_size is still used, so no change in your theme code): http://wordpress.org/plugins/optimize-images-resizing/ (github).
Maybe you could make use of the code to get around this restriction (by explaining the reviewer what it does).
My only concern is that some users wil expect a big new feature or change, just because we rolled over to 4.x.x.
4.0 certainly brings some awesome new changes and I am looking forward to the release, there should be no major issues for the authors as only a few (3rd party) libraries were updated.
Envato should either provide their own, integrated support platform, or offer an authentication via Envato account (oauth).
I’ll be there with some friends, my first WordCamp, should be awesome
You are going too?
I’m not sure you could achieve something like that without cropping the images.
I mean, sure, you could set up a demo with images that fit so it looks like that, but in the real world where customers use all kinds of images, I doubt something like this is possible (at leas not without some kind of scroll, either horizontal or vertical.
I might be wrong though.
To be honest, I’m not sure what’s the big deal about this, it could not be more simple to do this with jQuery.
If you have no knowledge of how to achieve this and you are selling templates/themes here, then I would say style switcher is the least of your worries.