Custom VO Lines

Couple of questions:

In regards to custom Voice Over Lines, does this void any kid of ToS within League (as its technically modifying game files that occur between the play button and the end of game screen.)

Secondly, if I were to create a custom voice pack for a champion, and were to add new lines, would this be played along with the other audio files, or is there underlying code that needs to be edited to include these? Along with this, is this the same case for VO lines that occur on purchasing certain items and champion interactions?

Lastly, assuming everything above is OK, would replacing the audio files in the game client with a file of the same name suffice to replace the original audio files?