How do you get from "I just think how it should work" to "discuss it with the senior members"? You've got notes, at the very least, that you've jotted down about the proposed changes. Guess what: that's the draft of a design document! If you've taken any reasonably thoughtful approach you'll have just a little more work to make it formal, invite formal comments and feedback, etc. Not weeks "drafting an architecture" document, just days (or possibly hours, if it's a small change). That's a small price in time to pay for such a big dividend down the road.