(I guess that you should ask Andreas about the state
of X-related things.)

Will do!

On the other hand, I'm pretty sure that most people use non-tiling WMs
and maybe we should think about them first. But I don't really think
that it's a right time for that. Because the distro isn't bootable yet
and there aren't too many packages.

I'm definitely interested in getting the distro bootable in general. What are the remaining roadblocks for this issue? What remaining tools need to be added? And the question for me: are there good, purely-functional implementations of these tools we can look at?

But what do you mean by "adapt for Guix"? What would you like to
implement? The only thing that comes to mind is to have shortcuts for
commands like 'guix package'.

That's a fair question. I suppose I don't much know -- the Summer of Code ideas site listed "package window manager" as one of the projects, so I assumed there was a lot to be done. Maybe that's more about packaging the dependencies of the larger projects.

It sounds like the proposed project has more to do with Guile than Guix.
But I haven't heard the details yet. Please elaborate.

The project would be about extending the Guix distribution with more Guile projects - it would not, admittedly, involving much work on the actual Guix package manager, though I'm not against doing work on that.