There are already third party utilities that inject dlls or monitor the mozilla windows to allow features lost when legacy extension support was removed.

I saw on ghacks the other day about ThunderBirdTray which is a 3rd party executable that watches Thunderbird to restore the functionality lost when MinimizeToTray stopped working.

Improved privacy, better download managment(DownloadThemAll what it used to be able to do), OS integration, ect have for the most part been eroded away.

Eventually things seem like they will escalate to the point you'll have to use CheatEngine, a suite of 3rd party programs running in the background, or special compiles of the browser made by 3rd parties like WaterFox or yourself to get chrome or firefox to do anything in addition to loading a webpage, and to stop it from doing a lot of unwanted things.