That file is a bit misleading. Adding a byte-code is easy; modifying the compiler is more work, and so is deciding what byte-codes to add and what they should look like.
I'd even go as far as saying that etc/TODO isn't necessarily a catalog of where new contributors should best direct their efforts.
That was what I suspected. I noticed that some items in the etc/TODO file seem to have already been (partially) resolved (e.g. Convert modes that use view-mode to be derived from special-mode instead).
I can see that adding a byte-code is the easy part. Modifying the compiler is definitely a more challenging part, specially to decide when the new byte-code should be generated.
Why don't you think of something that you personally would like Emacs to do that it currently does not, or doesn't do well enough? Or fix something that annoys you daily in your work? Such issues are never in short supply, and your time addressing them would be well-spent.
That is a very good suggestion. Currently I don't have anything that annoys me, the annoyances I had so far were easy to fix with existing features and were due to my lack of Emacs knowledge.
The reason I turned to the new byte-code item was to exploit it as a way to learn more about the inner workings of Emacs. I guess that I did already learn something with my modest investigation.
I will keep your suggestion in mind, and if I ever find something that could be improved/done differently I will reach back out.