Does anyone else? Is anyone else planning on implementing them?

First we need wait for support beforescriptexecute/afterscriptexecute by other browser than Firefox (unfortunately). But don't know if it will ever happen:

https://groups.google.com/a/chromium.org/d/topic/blink-dev/bChX6leKqtg/discussion

Fortunately, they are still existing in Chromium Dashboard (In development state):
http://www.chromestatus.com/features#5711871906676736

so there is still hope.

We don't have to wait for an implementation, indication of interest to implement would be sufficient.

Last year, I started the intent-to-implement thread on blink-dev and received mostly negative responses.

Since these events are only implemented in Firefox, and there is no interest in adding the feature in WebKit (https://bugs.webkit.org/show_bug.cgi?id=91463) or Blink (https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/bChX6leKqtg/Idut6cE4ORcJ), wouldn't it make sense to drop these events from the spec?

Rob, thank you, I created https://github.com/whatwg/html/issues/943 as a more dedicated discussion thread for what to do here.