Well, the system theoretically has all the tools to represent it well. I think the bare minimum for aiming for center mass being a viable default is to represent weapon accuracy (and inherent inaccuracy) as some form of minutes of angleThinking further about it, the "headshot problem" does seem to be unique to videogames. It's not like you get a lot of headshots IRL, so presumably if the system is set up to be simulationist it's going to mimic that rarity.
How about this: the targeting "circles" wax or wane depending on whether you're aiming for center mass or aiming for an appendage or head? And they wax less the more accuracy you have, and wax least for snipers?
and give the bullet a chance something else on a miss. It's already miles ahead in terms of realism compared to the straight up to-hit penalty for various body parts.
However, the majority of the problem is about the difficulty of hitting a moving target, and turn based already does a poor job at representing this (remember when people whined about 65% point-blank hit chance in EXCUM?).
I'd argue that PP already does it better than a whole bunch of other games, because its realistic bullet trajectory means the thing you want to aim for might just be momentarily obstructed due to the stage of the animation and firing angle.
A possible interesting bit of trivia, it seems vidya has been training people to aim for headshots and expect to get them. Not sure if it's been a problem for law enforcement and military training,
but the article seems to suggest that it may be the case:
https://onlinelibrary.wiley.com/doi/abs/10.1002/ab.21794
If so, the headshot fetish seems to be largely a videogame thing. There is one technique I know of called the Mozambique Drill, which recognizes that headshots are the definite way to make sure target stays down,
but even then making that shot depends on first landing two torso shots to bring the target to a stop.
I was thinking of the waxing/waning circle idea as representing shooter's skill within the system (as opposed to just the ballistics). IOW, a sniper being more accurate has a better chance of getting a headshot than a trooper, so when he aims for the head (i.e. anywhere other than center mass, which gives the ballistics the best chance), his targeting circle will wax less.
Think of it this way, as you move the targeting circle away from center mass, it grows bigger, or as you move it towards center mass it grows smaller. The degree of waxing/waning represents the shooter's notional accuracy or skill level - so a sniper's targeting circle will grow only slightly as he moves away from center mass, whereas a grunt's will wax bigger.