Would the notification system not work, where it can be configured to send you an email of the new post?
I'm kind of confused on the "store the thread temporarily" bit as threads don't have an expiration date...
An example:
"Oh boy oh boy a new thread! I can't wait to read all the things! Oh no, I gotta pay attention otherwise my bright and awesome future will be ruined! Lemme just click the handy-dandy 'Read Later' button and get back to work."
An unspecified period of time passes.
"Wow, that was super educational and fun! Now, what was I gonna read again? Lemme just check my 'Read Later' list and.... Ah yes, 'Herken: all the things', lemme click on it and be redirected to the thread."
This would also be handy in a situation where you're all like: "Oh gosh, oh jeez, all these topics that were posted but I only have so many eyes! Well, I'll just click those "Read Later" buttons and have a nice list I can work my way through one by one."
It's not the notification for replies to posts, it's some way of putting a thread in a list.
If you subscribe to that thread, its someone like a read later as well
Subscribing to a thread is fine, but it won't show whether you've already read it or not. Following threads is more to get notification when a reply is added, less for managing which ones you have and haven't read.