I the next version of iOS, the iOS 10, you will gain ability to remove stock apps from iPad, iPhone and iPod Touch. So instance, I do not do stocks so currently I have tucked it away in a folder like I am ashamed of it.
Same goes for Watch app on iPhone which is useless for me since I use a Rado watch and want a mechanical watch to tell me the time instead of childish digital watch. Other apps that we are tired of is the atrocious Apple Maps which is not as complete as Google Maps both in terms of maps detail and application features. You will be able to delete that as well and gain some free space.
Same goes for iBooks or Podcasts app that do nothing but clutter up space and screen real estate. That said, if you miss a particular app, you will be able to download it from app store. Apple does say that removing certain apps will lead to system functions or information. For instance, when you delete weather app, it will remove weather info from notifications as well as from that stupid Apple watch.