Quick update: Kate tells me that during every single stream I do, at least one person asks how they can remove or change their queued request. You've never been able to do that: once your request was in, it was in forever, unless I caught you asking about it in chat and manually booted it from the queue for you.
No more! Now, when you make a request while you already have a request in the queue, you will be asked if you'd like to update your existing request. If you choose to do this, your existing request will be changed without losing its position in queue! Should make a lot of people happy.
There's still no way still to straight-up remove your request from the queue, but I think 99% of the time people want to do that, they just want to queue up something different, anyway, so this should please just about everyone.