Yeah, I played with Silverblue for the first time a week or two ago, when I decided to move back to Gnome from Plasma. When I realized that I'd need to layer adw-dark to get rid of the light settings panel in Gnome Console, and then layer in aptx and ldac support, and then some drivers for hardware accel in Firefox... I came to undestand that truly approaching this as minimally layering, and instead properly relying on flatpak and toolbx/distrobox wasn't going to work out. Instead I'm just going to get anxious every time I have to say, 'well fuck, I guess I have to layer this too.'

That and I really don't like the mess of a filesystem. So back to Arch, with some things learned to keep stuff I don't like out of my base system. I can use a Bazzite-Arch container for Steam, to avoid having to enable multilib, for example. Well, if I can figure out the performance issues, anyway. And I know I'm weird, but I'd kind of like to avoid using AUR on my base system, and Flatpak kind of terrifies me for the reasons you mentioned

I do look forward to an immutable future, but I don't think it's going to make me happy for some time. Maybe Nix or GUIX, but that sounds like a winter project. I know some folks use an Arch base with Nix layered on top, but that rather sounds like the inverse of what I'd ideally want. It seems like the beauty of Nix is that you don't have to worry about layering, because YOU declare the base?