While one can do these things, and I for one think it’s fantastic that julia allows this, there’s a different answer to whether or not you should. Non-standard solutions to things as simple as indexing make your code less readable / reproducible.
If you have a type defined where there’s a well-thought out and compelling reason use non-standard indexing syntax (as is the case for eg DataFrames), that’s a different matter, but in general I think it’s not a great idea.