Alot of people I know did too, Coprone. Happily I never used the trainer myselves but I only asked for hacked money so no ban for me.
Marty, the reason they don't want alternatives to MP is because of sharkcards.
Rockstar and TakeTwo make a hella lot of money from sharkcards, and if anyone makes an mp that doesn't require sharkcards, most people will move to that which will result in a loss for Rockstar and TakeTwo.
Altho it will hopefully be possible to have better FiveM in the future, even if Rockstar disagrees.
All they'd need would be a way to bypass the Social Club system, altho then it would become an illegal mod.