I likewise have a fair number of Alexa units. I agree on your points 1-4 and don't share your perspective about 5.
Video watching is random enough that I don't see voice control being something I'd tolerate using. Sure, turning the TV on/off or selecting sources might be useful, but NOT direct program selecting, let along ffwd/rwd features. But I wouldn't argue against it being available as an option for others.
I very much dislike that I can't control timers from other devices. As in, timer in the kitchen is going off but I'm across the house and my local Echo can't cancel the other. Likewise, I can't set a timer or alarm from one unit to be heard from another (or several). For example, setting a wake up alarm for the kids. Or a go-home-before-you're-late alarm for kids down in the rec room.
Don't get me started on the disaster that is setting up devices on the App. It's just... awful. No decent sorting, no multi-select for grouping and NO BACKUP. I'd put up with some of it if they at least offered a browser interface to make it less tedious to use. Scrolling around in the app when you've got upwards of 200 devices is just terrible.
I'd sorely like to have a way to list what devices exist in a room. I can't always remember what a light it called. Master bedroom lights, for example, ceiling cans, ceiling fan light, reading lamps on left/right, table lamp, etc. "Alexa, what devices are in the Master Bedroom?" would be darned handy. It is at least somewhat smart about responding "I have multiple devices named Master Bedroom, which one?". How about "Would you like me to list them?"
As for audio, I'd love to have an option to redirect only some of the audio stream. As in, music out the Aux port but keep Alexa messages on the device itself. Or via BT. It's helpful to have the device as a focal point for requests/responses, especially if the music is cranked up loud.
Now, if they'd just figure out a way to get my Dot to pair with the radio in my Porsche...