So you want to report people for leveling additional accounts?
Circumventing a ban, fine, that makes plenty of sense. The standard of proof would be massive they'd literally have to say something to the effect of. "Riot permabanned my main for trolling so I just made a new account to troll." The likelihood of that ever happening is so astronomically low that it wouldn't really be worth pursuing, and besides if that hit the tribunal they'd get hard punishments anyway.
Furthermore I can't comprehend how you'd want to report people for smurfing, typically people are just climbing the ladder again, and yeah it sucks to get roflstomped by a d1 ADC vayne main, but there's not really any way around that, and to ban people's accounts for it is just asinine. Again the standard of proof would have to be massive, and there's an astronomically low chance of that happening anyway.
Furthermore if someone is trolling, spamming, toxic, etc. There are already options to report said offenses in the current system.