This has been requested by the Nin community for so long so I'm hoping that one day an update will fix this problem. The bubble pipe and fan is intended for Fan users and Bubble users, but players that use elementals/int medic are able to put a small amount of points into Str and gain so much advantage off PvP due to it, to the point where most of the fan/bubble tool users (mainly bubble pipe users due to them having less/weaker weapons than fan) are mainly elementals/int medics. The fact that there's more elementals using a tool that's invented for hidden mastery users shows there's a problem. Many people have complained about it specially Leaf ninjas due to the fact that they don't have a tool that they can use unlike the other villages, and due to the fact that the mist village (for example) has elemental/int med users that majority have pipe tool and tend to spam the snare which leads to snare spam and free/easier combos to land. I've seen some people suggest that Leaf should get a tool for GF but the mastery is already broken/easy as shit to play, plus making more braindead things isn't the best way to balance things out, Which is why I suggest 2 of these options.
1. Make it so that players can't use elemental/int medic jutsus while having a pipe/fan tool equip, this should be easy to do since this is already added for Gentle fist users not being able to use their jutsus while having a Weapon equipped, This wouldn't completely remove all pipe/fan tool elemental/int medic users but it would be a good nerf.
2. Make it so that when players choose their mastery (Ex: a Sand ninja picks Wind as his mastery) They have to pick between either Int (Wind/Water) or Str (Fan/Bubble) that way they can't learn Str Fan/Bubble jutsus as a Int Wind/Water and vice versa.
Problem with number 1 is it doesn't fully remove the problem, but it's a good nerf that might end up making some players drop their pipe/fan weapon.
Problem with number 2 is some people tend to enjoy elemental/str hybrids (when I mean hybrids I mean ACUTAL hybrids not people w 20 Str) so they would lose out on mastery combinations that would at least cause them to risk their stats far more than a regular 20 str tool user.
I'd honestly stick with option 1 for now since it's an easy add on but anyone can throw in a better suggestion if they can since it's an open topic. As for Gentle Fist this post right here explains a good nerf for it, so Gentle Fist nerf suggestions can go in that topic as well.
Shout out to @Black Rain for the post idea.