There are no insurmountable obstacles to what you are asking. At least none that I can see now, but I do see some things that wouldn't be convenient. First, wh

There are no insurmountable obstacles to what you are asking. At least none that I can see now, but I do see some things that wouldn't be convenient. First, when using other commands one should be able to input in bold as well. For instance, while searching. Otherwise, one wouldn't be able to search for the bold version since it is encoded differently. Second, search and other commands should be aware that "f" and "𝐟" represent the same letter. Otherwise, each search becomes a game of trying all the styles to see what gets results. Third, and this is a matter of taste, I prefer to keep the presentation separated from the structure as much as possible. I much rather write \myStyle{fun} and keep writing. Later, when the writing part is done, I can define \myStyle as bold or whatever makes sense.