What's most amazing is how easy it is to switch kernels on NixOS as this article touched on. This prompted me to switch to Cachy kernels, and after some caching delay (apparently need to switch once before caches set) I was able to take advantage of a completely different OS's core strength. Truly the one OS to rule them all.
That's how I manage all of my virtual machines: building an ISO from a NixOS config and booting it as a virtual machine. I'm going to take some time to see what bits of this I can copy to slim down my ISOs.
One additional benefit: I build all my software from source (by disabling the nix cache) so stripping out these extra programs will not only slim down my ISOs but it will also reduce the build time.
Curious bout your use case for building all software from source, is it because you're worried about the supply chain since nixpkgs builds don't have reproducibility guarantee?
I was already building the vast majority of it from source because I enable CPU optimizations for the specific microarchitecture in the machine (nixpkgs.hostPlatform.gcc.arch and nixpkgs.hostPlatform.gcc.tune), so once I learned about the risk of supply chain attack on the nix cache, disabling it entirely was a pretty small change.
So far, I'd say the biggest negative (aside from the build times that I was already experiencing due to the optimizations) is that GNU savannah will temporarily IP ban you when you download too much from them. For example, building the grub that is used for the ISOs downloads like 70+ patches from GNU Savannah which frequently triggers the IP ban.