BurningSmileValve should implement a cpu id based ban system like over watch. You cant fake a cpu ID like you can IP bans. This would prevent users from just spamming alt accounts as there is no way to change your cpu id, its built into your cpu so the only way around it would be to replace your cpu. (Most hackers are kids that dont have the money to replace their cpu.
or just make the competitive pass more expensive, no one really needs an alt account and most people do have phones so matchmaking is free for them.
the only people that might need to buy it are people who chose not to have "decent" phones or cheaters who may need an alt account. and I doubt that cheaters will buy competitive passes just to get banned again, valve just needs to actually keep up with the cheaters so they will get banned after using cheats relatively fast and eventually they'll run out of money or will to cheat.