So why can't that change be introduced? It seems, as you say, maltman, to be a simple change to make.
I don't know. My best guess is it's not Era Accurate and the server owner doesn't want to make any PVP aspect of the shard feel all "customy". Players expect a very traditional free-shard PvP experience and perhaps "Headshot" sounds like something that belongs only in one of those 30 population servers that no one plays. Just a guess. If the fletching changes that are incoming include repair and runics then that's a step in the right direction, albeit a small one. I still feel like headshots could be a lot of fun. They could do 5x damage in PVM (10x vs ettins... 0x vs headless ones). They could apply a simple curse stat affect on other players, and if someone is killed by a headshot, maybe their head could fly off in a random direction and have a special trophy-name like "X's head. Shot through the eyes by Y".
I have not been here long, but one of the attractive factors of this server is that it is more or less an era accurate representation of UOR as it was during 2000-2002. I assume there are quite a few of us with that mindset. Alot of these special moves and things you suggest were added during AOS and there are plenty of high population AOS servers available. The main issue with archery seems to be that it just doesnt do enough damage. With a vanq bow i average 20 dmg shots vs armored players. During UOR you just hit for alot more then that (with a gm bow mind you!) - the reasons why can be debated endlessly, but thats basically why archery isnt good. A spear hits for more and has para blow, and thus is infinitely better for most situations.
More damage would be great. Ag bows do great damage but they cost a lot! I have yet to see a repond slayer bow.