Why can we not report players with evidence?

Something that has bugged me is how we are only able to report players in the post-match screen. Why is there not a feature to report players in the forums for Riot to look at where they can get screenshots/video evidence of such players when they use hacker methods? I had a Cassiopia in my last match that was healing without healing items or spells every single time she was about to die keeping her alive when every other player would have been dead. I have no way of getting this kind of player a proper report if there is no way to submit any form of evidence that is not in the chat log. I feel like this is a major flaw in the reporting system and it upsets me that a immoral player like this Cassiopia gets to roam around the game and there being nothing anyone can do about it because nobody can submit any form of physical evidence.