Entirely possible just need to extract the required files and then edit them.:)
https://github.com/slashiee/StreamTool
helps convert the bfstm sound files
Found some information on the file format http://mk8.tockdom.com/wiki/BFSTM_(File_Format) ,
as well as a tool by @AboodXD https://github.com/aboood40091/BCFSTM-BCFWAV-Converter but when going from Wii U .bfstm to Switch it only changes the header file so for a fix I have Found is using 010...
I was trying ARMS as well with LoopingAudioConverter it works but ends up formatted for Wii U(big endian) not for Switch(little endian) so it doesn't work in-game.
Tried to edit save for arms on HxD but it seems to be encrypted as edited save inject just gets cleared not sure what I can do to decrypt the save so the game doesn't clear the save file