Regarding the last paragraph of the post:
I know modern Android helps me when I'm low on space, and would like to see that in Windows.
Just this weekend I used the Free up space now option under Storage settings in Windows 10. That's a step in the right direction.
Here is a link that talks about it. Link to HowToGeek
I haven't heard of reserving space with dummy files before today. (Granted, I'm still new at this.) That's an interesting idea if admin that handles storage isn't around to assist.