Most of the fireworks ninja you are suggesting are very obtainable, some of them could be put in consideration like taishao period but you are asking fr way to much from fireworks event.

1. Sasori [100 Puppets] It is 400 pulls in Sage Naruto Treasure, it was never unobtainable.

2. Minato [Hokage] I have seen it for redeem everytime in "Fateful Choice" Event.

3. Itachi [Anbu] Very easy to obtain in Monthly Event (I have him 3 stars and have an extra 55 frags for 4 stars)

4. Kakashi [Susano'o] It was in last weeks "Lucky *" Event in the wheel you could obtain 15* his frags per spin. (I saw many people have him)

5. Iruka you can obtain from extra fragment refine I think. Other ninjas like Utakata [Edo Tensei] Hinata [Cloak] Danzo [Izanagi] I have all seen been recently added in redeem shops.

I could go on for awhile listing ninjas, but I hope you get my point.

Fireworks Event makes it obtainable to everyone im not saying its a bad thing but all those ninjas?!?!

Fireworks Event should only have never before obtained ninja for the prize Example: Dan Kato [Edo Tensei], Minato Namikaze [Suit]. These ninjas were almost never seen before and nobody obtained it and now everyone has one.

And about the ninjas they haven't added very often like taishao period ninjas, suit ninjas, and some retired old ones that would be very reasonable to add back once in awhile.

If you want ninjas like I mentioned above about the fireworks event, just save up coupons lol, I recently obtained Kakuzu [Earth Grudge Fear] and almost Minato Namikaze[Hokage] (68 Frags).