I think it would be a massive feature change if Bootsrap or uikit css frameworks were integrated with PixelExit themes. They offer unique components like slideshows, modals and other features that the default XF does not offer. Sure, these things can be styled or added on an individual basis by skilled themers, but it would be great if they worked out of the box. I've toyed with the idea before, and I think I've asked here before, too - but didn't have much success.