Off the top of my head, the only f2p ninja I can think of that are useful are WB Asuma, Kazekage Gaara, and Gakido (depending on the ninja you're using.) A lot more should be useful. Make it so they can fight some of the event ninja. Not only used as support useful. If f2p ninja were can be used to fight event ninja instead of just support. I think this game would be way more lively. Change most of the breakthoughs so they can. I get that the low power people can't fight whales, that's just obvious, but if two low power people are around the same power. One has event ninja and the other doesn't, during pvp, the one with event ninja is always going to win. There is nothing the one without event ninja can do. If the one without event ninja can't ever do anything, most likely wont have motivation to keep playing the game. If they can have a chance against people with event ninja, it would keep them more interested in the game and play longer to get event ninja and some spend money on the game.

I think the f2p ninja, if you build a good team, you can stand a good chance at fighting someone with event ninja. Not saying to own them, but have a shot at winning.

Also, Im saying this as someone who wants to help others out. I have plenty of event ninja.