There could be security issues with a "cat" command, which is why we once rejected the idea.
Note that the server can entirely control the console via CSQC or via stuffcmd, and also we have multi-user rcon. All of these can run console commands, possibly get output - apart from tab completion's output. This is why the console is so restricted. And "cat" would provide a way to show the currently set rcon password on screen, for which there is currently no way (as the cvar display refuses to show it). This also means, a rcon user can retrieve all other valid rcon passwords by a single command.
This is why special keybinds (e.g. tab completion) currently are the only way to show rcon_password. And it should stay that way.
However, coding a text editor control for menuqc would not be dangerous in such a way. Only a lot of work to do
It would be a very welcome addition for sure...