Actually, I think it was possible for Solus when it was just Budgie as their DE, and they kept strictly to their curated packages.
Like Days said, they do generally limit their packaging to just one or two applications that do the same/similar jobs. For instance, originally the only file manager in their entire repo was Nautilus. No pcmanfm, Nemo, Caja, etc. I seem to recall reading a forum request for Nemo to be packaged - I think it was refused.
But now they have added other DEs like MATE, Gnome and possibly Plasma in the future, so the repo also has Caja and Dolphin file managers as well. And by opening the doors to more DEs and of course as they generally add more applications to their repos, there will be more packages to maintain and the potential for problems increases. Esp with Plasma being actively developed and different from the other 3 gtk3-based DE, updates could be more tumultuous.
We’ll see how successful they continue to be in having a maintenance-free rolling distro. I hope they can do it but I think they need to keep tight control over what gets into their repos, which means lots of work for the dev team.