@DuoForce You might take a look at suloku's Gen 5 Save Tool. It has some of those features that are not integrated into PKHeX yet (like Entralink Forest editing).
For C-Gear/Pokedex Skin and musical injection there's an English translated version of PokeCGear from PokeStock https://projectpokemon.org/home/files/file/2506-pokestock2/
Other programs already support editing these things (PokeStock can do all the above), hence it is not a priority for me. Current generation games end up taking most if not all of my time devoted, but I do accept pull requests / revisions if anyone else wants to add the functionality themselves.