So maybe I want to play music, or watch some TV and have the computer sleep at 9.30pm and then wake up in the morning to play me a tune for waking up.

I use KAlarm, but you can schedule any way...

window_list=$(wmctrl -l | awk '{print $1}')
for window in $window_list; do
    wmctrl -ic "$window"
done; amixer set Master 10%; systemctl suspend

I set the volume because last month, I left my mouse on and the computer woke up at 3am and I got a few noisy notifications.

Basically, whatever window is open/playing will get closed so that in the morning, it wakes up with a tune which also helps me remember what day it is.

I made an account just because I wanted this feature. :')

And I don't think it's hard to create. I mean, if the developer really doesn't have any time, they can make sure that they use a preliminary command like "sleep 60m && pkill strawberry" at first then develop this later. (I have been doing this anyway on my systemd Linux Laptop) Not sure how it would work for other operating systems tho