This does get into the idea of portability of code and the "linuxism's" that are being put into some mainstream projects.
I have the sense that many of the daemonforums and FreeBSD forum participants prefer smaller, lighter window managers.
Systray applets are attractive to me in that they are modular: don't want it, don't install it. For myself, the systray applets that i am interested in are volume control/muting for all systems and for laptops battery and network managers. I have not been able to test the tint2 battery applet in any BSD and the one in fbpanel is reported broken.
Both volumeicon and gvolwheel appeared to be modular in that alsa and oss functions appear to stand alone.
gvolwheel codes for gnome-alsamixer to be the default mixer (even in FreeBSD) but the end user can changed the default mixer in the "preferences". The mixer interface I like in my OpenBox/Tint2/Wbar desktop is aumix run interactively (aumix -I). Aumix is another app that in OpenBSD uses an OSS backend.
I do not know if it would generate any enthusiasm but coming up with a lightweight, modular BSD friendly desktop using the model of the LXDE project would be answer to
individuals who are steering software development away from BSD desktops.