iMessage's missing killer feature

Apple should give users the ability to subscribe to text threads. Here's why. My family has an ongoing text thread with 20 members. Sometimes the thread deteriorates into something i care nothing about and litterally 100s of messages that i dont care to review pile up in my inbox. Why is this an issue? Its a nuisance for at least two reasons. First, the notifications are annoying. I cant get rid of them because I dont care to disable notifications on the messages app. I could put the conversation on mute but still that red badge shows me there are new unread messages. The second reason its a nuisance? The rich media messages accumulate on my phone and take a dent out of available storage. Again, I i want to save messages on other threads. So i wont configure my phone not to save all messages. For me, this nuisance is bad enough that sometimes i leave the conversation. Leaving a conversation on an iphone is not costless to undo. To rejoin, someone must add me back. I can either wait until someone eventually adds me back, or i can ask someone on the thread to add me back. This is a real pain. Solution: let me subscribe to conversations.