There is a "hidden" feature for footsteps sound in this particular mission pack, it doesn't work for Quake 1 or Dissolution of Eternity.

In order to hear footsteps in Quake: Scourge of Armagon you need to:
1) install Quake (GOG or Steam)

2) run Quake: Scourge of Armagon

3) open console (~) and type "CROSSHAIR 2" (sic!), restart the game
alternatively you may simply add line "crosshair 2" into config.cfg file in quake/hipnotic folder

4) enjoy the mighty footsteps from vanilla game
Please note that you'll hear footsteps when you start or load a game, for some reason demos have no footsteps sound for protagonist.

DOS Quake, glQuake and WinQuake versions were tested.

Proper shortcuts:
...\Quake\Glquake.exe -hipnotic -game hipnotic (glQuake)
...\Quake\Winquake.exe -hipnotic -game hipnotic (WinQuake)
...\Quake\DOSBox\DOSBox.exe -conf "..\dosbox_quake.conf" -conf "..\dosbox_quake_single.conf" -noconsole -c exit (DOS Quake)
for DOS Quake you may want to tweak dosbox_quake_single.conf file in text editor.

P.S. There is no need to specifically indicate parameters "*quake.exe -hipnotic -game hipnotic", the default "-game hipnotic" should be sufficient. However don't forget that second mission pack will have wrong cvars for ammunition if you'll not add "-rogue -game rogue" after execution file in command line.

Finally it works!
I've been curious how Quake would feel with footstep sounds! =)