Your suggestion isn't bad but it's too complicated. I am agree with check post is plagiarized or not. But check ban user really not easy task for every post that we want to send merit. It will be more better if ban user mark by forum, so that easily we can identify before send merit.
A good post is a good post even if its author has been banned or is a scammer or wears socks with sandals.
Obviously, good post is good post. But sending merit banned user is useless. Simply you can send it another good post. But problem is we don't know who has banned. And we don't have much time to identify that. So I am not going to check this every time if I have no doubts. Especially once I use mobile.
But I always visit history once I send merit to newbie. If a user totally newbie and he haven't receive single merit yet then I have doubts about his post and I always visit his history before sending merit.