Yeah, the only real feature request channel is to be big enough on Twitter that Elon notices your tweet.

But yeah, the alert sound was for if you were starting to move into a lane with a car. I guess Tesla want you to pay for the FSD package that includes the functionality that allows the car to change lanes when there's a gap so you don't have to worry about blind spots and the car handles it for you. I have this feature in mine (due to the no longer available Enhance Autopilot package)… but I will still check the mirror and camera feed myself before letting the car do it. One handy feature of this is that it kinda has what you're asking for - it will bring up the camera feed for that side of the car before turning on the indicator or attempting to move itself.

To its credit, it has never suggested moving into an occupied lane, nor has it moved when I've manually told it to do a lane change when there was a car there.