Same situation on XFCE desktop and this is what I did to remove bluetooth completely and eliminate the tray icon.
# disable bluetooth service
systemctl disable bluetooth.service
systemctl stop bluetooth.service
# suppress driver (lsmod)
echo -e 'blacklist bluetooth' >> /etc/modprobe.d/90-no-bluetooth.conf
echo -e 'blacklist btusb\n' >> /etc/modprobe.d/90-no-bluetooth.conf
# do not start blueman tray app. append Hidden=true
nano /etc/xdg/autostart/blueman.desktop
# disable bluetooth in pulseaudio comment lines (#).
nano /etc/pulse/default.pa
.ifexists module-bluetooth-policy.so
#load-module module-bluetooth-policy
.endif
.ifexists module-bluetooth-discover.so
#load-module module-bluetooth-discover
.endif
# remove packages with no dependencies
pacman --remove --nosave blueman