I understand your thoughts exactly.
What will help with future maintainability and reduced breakages is picking something with low / stable dependencies.
Go to
https://www.freebsd.org/ports/ and type in a bunch of DE names:
Gnome has a frightening 592 dependencies hahaha
Xfce4 has 243 which is still a sh*tload.
Lxde has 194 which is still too many for something that should only need a GUI toolkit and nothing more.
Lets look at non Gtk+ / Qt DEs...
CDE has 41 and looking at them they are pretty much just X11's standard packages, with motif. Nice!
What is also nice with CDE is that the entire desktop is in one source tarball and is very easy to build.
I personally like the look but I realize it does look a bit dated. It however has stood the test of time and is likely to outlive many current desktops so if that is important to you, I say go for it. Something that has good support moving forward is bound to look dated one day anyway.
Or... make the UNIX terminal your desktop and you only need a dependence on XTerm (which comes with X11). It sounded stupid to me at first too but learning to be comfortable at a command line is the most useful thing I have done. It has arguably one of the best text editors there (vi) and along with tmux, it provides multiple "windows". This will likely be around longer than our lifespan too if you want something looking forward