Hi Meow, welcome!
Unless your suggestion is added upstream I don’t think EOS-devs will bother to implement this.
I personally also don’t think it’s necessary 
. If you choose btrfs as file system in calamares it will already be set up with the subvolumes @ and @home. All you need to do after the install is to manually install Timeshift or Snapper, that’s it.
If you need any help or suggestions in setting this up in EndeavourOS there are already some Wiki articles and forum posts.
For example, see:
- BTRFSonLUKS Wiki Article (quick version; verbose version)
- Forum Instructions for unencrypted setup