About the whole new type thing, to be fair, during the whole Light and Sound theory spiel, a lot of people said that seventeen types is enough. Then we got Fairy. I do agree that the Fairy-type is still fairly new (I swear that's not a pun, trust me), but I want to do the new types for fan games that I'm planning to do, NOT as speculation for the future. The ???-type (or Problem-type as I call it) is just impossible to put in official lore and contexts due to it's design, and I believe we got our answer for the Sound-types future in the shape of Noivern. I still believe that to this day, due to it being a bat and lurking in the night, it's a double play on words and design when it's literally the "nail in the coffin" for Sound-types.
As for the other things:
- I agree with Shedinja. All the way. 1 HP doesn't help it though...
- The way you put it actually makes the Ghost/Fairy typing pretty balanced. It's basically the same situation with Eelektross. It's zero weaknesses seems like a dream come true, until you see it's number of resistances and it's Speed.
- I can see your point with Psychic being weak to Dragon, it is a necessity in this case, I just find it funny that now the almighty and powerful Mewtwo will truly cower in fear to the true overload and master of our realm, Sir Goomy.
- I may be alone on this, but I actually don't see the Fairy-typing in Mimikkyu. I do love it's design though, it's creepy and adorable. The perfect combination.
- I did a double check on the type combinations, and there is one other type combo that should be looked at: Normal/Ghost. By this type chart it also has no weaknesses, but it has resistances to Poison, Bug, Steel and Fairy, has three immunities to Normal, Fighting and Ghost, and it's two stab options are pretty threatening. The only solace I can see is that the only way to get this typing in battle is with Trick-or-Treat, but the typing could possibly appear in the future.
Hey, since we're in the discussion for type chart changes, could you take a look at my version? It's not balanced number-wise, like you did, but I really tried to take other factors into account, like moves and abilities and what not (for example, this type chart assumes that all entry hazards now have a 5-turn limit, which I also plan to do in the fan games), so I'd love some sort of feedback from it. And yes, the Sound and Problem types are there, because of reasons previously stated. I will say this though, the ???-type does seem broken on the outset, but that type is planned to have a very low average stat total. Like, legendary ???-types would probably have stat totals like 500-535. The offensive coverage is also planned to be vast, but uncommon. A.k.a. most Pokemon can learn them, but only about two or three, at the most.
Here it is: https://docs.google.com/spreadsheets/d/1j3MT2DwS_wmG4iI0OW65Woc1lBYy1i6pRApVwty6gfw/edit#gid=184606815