No one has ever said that there's no penalty to use Option 4. In fact, the GM needs to set the penalty if a player wants to use option 4. It's not a philosophical loophole. It's part of the Regeneration rules as written. Just like shooting a tire or shooting someone to knock them off a ledge. The GM has full rights to veto it, and it probably will run smoother if the player volunteers a penalty ("I'll try to hit his head, and since it's a humanoid target, that's a -4, right?"). It's not metagaming unless the character has no idea that a headshot will work well against a regenerating target but the player does. Even then, if shots in other body parts don't work, the PC can try a headshot as a "well, here goes nothing" situation.
The game doesn't explicitly say "don't apply a penalty for option 4". In fact, all of the uses of option 4 in canon so far indicate that you must apply a penalty. There is no evidence that the penalty can be equal to zero (although the tables indicate -variable), although there is no evidence that it cannot be zero either (again, the table). You still burn a Free Action to do it, and although that's the smallest possible action cost, it's still a cost. You can't use that Free Action for anything else, like dropping prone, ejecting a smartgun clip, swear, etc. Remember, you don't get an unlimited amount of Free Actions any more or Free Actions for every phase as in previous editions (you only get one Free Action per Initiative Pass in which you have an action, SR4A p 65).
The game doesn't explicitly say "don't apply a penalty for option 4". In fact, all of the uses of option 4 in canon so far indicate that you must apply a penalty. There is no evidence that the penalty can be equal to zero (although the tables indicate -variable), although there is no evidence that it cannot be zero either (again, the table). You still burn a Free Action to do it, and although that's the smallest possible action cost, it's still a cost. You can't use that Free Action for anything else, like dropping prone, ejecting a smartgun clip, swear, etc. Remember, you don't get an unlimited amount of Free Actions any more or Free Actions for every phase as in previous editions (you only get one Free Action per Initiative Pass in which you have an action, SR4A p 65).
Okay, I can see that, but I have a problem with the comparison here... If I want to shoot someone in the head and ignore their armor (they have no head armor) then Why would there be a greater penalty to that than just shooting them in the head... can you answer me that one... because it quickly becomes logically inconsistent... IF there is no armor on the head, my called shot using option 4 (lets give it a -4 to hit shall we) is easier than using option 1 (with that annoying -8 for the Armored Jacket)... this should be consistent, and yet it is not... on one of those shots (option 4), I will have to contend with armor (Soaks with Body + Armor), even though there is no armor protecting the head; on the other option, Same basic scenario remember, I will incur a penalty to hit the unarmored head, and not have to contend with the non-existent armor in the soak test (Body Only)... this is logically incompatible as in both cases, there is no armor protecting the head...
If you ONLY use option 4 for "incidental" secondary effects (I know, there is that word again) and then option 1 for actual targeting of the head for damage, you will never run into this inconsistency, the only time that it will become more difficult is when the target is actually wearing protective covering on the head itself... Thsi leads to better playability as then people will not game the system... the options will then stand out as tactical choices that are relevant...
You may not agree, but there it is...
Keep the Faith