if its bland and watered down I doubt it is going to make a big difference so I wouldn't bother sending it. Although I'm also not sure what you mean by saving it for later.
I'm worried that if I send it now, I will have nothing to send if/when I am put on a waitlist.
I've never understood why people think an extra mediocre LOR would help for a waitlist. Your best strategy to get off waitlists is to raise your GPA (if still in school), raise your LSAT (Feb or June), and show interest with LOCIs and perhaps campus visits.