Using GNU Guix to build can solve the "difficult to install" issue and also help with dependency management, however compilation time can't be avoided. Advantages remain, however, thanks to package transformation options!
I do use it, as it's the default kernel of the GNU Guix distro which I use daily.
The main drawbacks is that it forces you to choose your hardware wisely, using e.g. h-node.org to be sure it's compatible. Otherwise, this is quite exactly the same kernel, just really free as in freedom.
The main difference with NixOS is that it's fully free. Another difference is that the language used for configuration in Guix is Scheme, a general purpose functional language.
It would give an enormous power to who controls this "front page". This page could restrict any user arbitrarily, lock them out, spy on them, etc. And because this page would be unique, they would have no alternative. This is exactly why federation is a key to freedom.
No more.