I originally had this idea as a part of a different proposal but then I realized that the system I was proposing was overcomplicated and had no precedent to exist. As of now my conviction is that it will not see the light of day. However, I still liked this part of it, so I am adding it as its own proposal on the forum.
Basically, the idea is that the “source sample tool” mount uses that icon because its mounting a tool that has no icon of its own; the sample tool is used as a base to make other tools. So, I then wondered what that tool might be. In the end, the idea that stood out to me as the most fun and fitting was that the tool allowed the player to see invisible level geometry. Meaning, stuff like info_player_start, which is normally invisible, and env_cubemap, which doesn’t even have a 3d model. Having the sample tool mounted would allow you to see these parts of the map which normal players cannot, which can come in handy on unfamiliar maps, especially when the mapmaker has hidden a secret.
I also think it would be very interesting to have an event where players have to infiltrate a specific custom map in the void, but having a sample-tool-wielding player would be necessary to figure out the puzzles, as they can see triggers and math_counters, allowing them to work together to determine what the puzzle is and what the map logic is for. This also brings an opportunity to have special entities that can only be seen by those with the tool mounted.
Also, I just really like the hammer editor icons. They have a distinct vibe to them that I enjoy and find fascinating. Adding env_cubemap as an emoji to 333 software was my idea.
I understand if the source sample tool mount has a different intended purpose. It already has a precedent of doing nothing in normal gameplay, anyways. If that is the case, then this functionality may live on as another mountable tool, obtained in a different way. It could even be a physical weapon rather than a mount, if need be.
Thank you for reading my proposal.