You might be over estimating the impact of a forgotten app. This situation has already been taken into account in the design of Android.
Recent versions of Android have introduced app hibernation. This is a special application state that's triggered when an app has not been used for months, meaning the app is not likely to be important to the user. When an app goes unused or forgotten, Android wipes out all the application's caches and temporary data, revokes all important runtime permissions like location and file access to protect the user, and blocks the app from running without your explicit request to make very sure it can't silently leach your system resources.
Apps you don't use are effectively frozen automatically.
Long before hibernation kicks in, Adaptive Battery already severely punishes applications that the user doesn't use regularly. Within a matter of about two weeks the app will lose the ability to run in the background unless the phone is plugged in and charging, and finally hibernation will kick in to deliver the killing blow until you either launch the app or uninstall.
Feel free to load up on useless junk!