Reread the post and I can understand the argument about "dumping down" things...so let see.
The lore is basicly that with rising heat the onboard computers and mechanics aren't able to keep up with the pilot of the mech.
So while you might have the best pilot with 100% aim he can't do nothing without a good firing solution from its onboard computer and the arms/torso beeing lined up correctly.
In TT they use modifiers for Range, Movement, Heat and on top of that a hit-table to find out where you hit the target.
So how to represent this in MWO?
Hit-table:
I think this is hardly doable. Sure you could make it so that the game internaly calculates a hitzone but hitting (visualy) the torso and getting a damage in the leg is very off. So the hit-table dosn't work...and I think thats ok.
Movement:
I think we don't need a modifier here. Running around and hitting something is allready complex enough. This shouldn't modify targeting. It also rewards good players for investing the time to become that good. (High respect for some light mech players. I allways puke when I see you in spectator mode

)
Range:
The further away something is the harder it is to hit. For this a very narrow cone could be used. It would be in a shape that at close ranges you might hit a bit more left or right but you still hit the zone you targeted, like it is now.
Over medium ranges you might hit a zone left or right of the target, like aiming at the LT and you have a chance to hit the CT or LA. Long ranges is where its more about hit or miss. A quite wide cone that realy gives you a risk not to hit at all.
Another option could be falloff damage to all directfire weapons (Laser, PPC, Gauss, IS AC) and more spread to SRM, LRM, Clan AC....
Point is that ALL weapons would need this without exception.
To me its a pretty uninteresting option because it dosn't solve the sniping/alpha issue as good IMO and dosn't create a risk/reward system where I have to decide between going in closer or try to get the "lucky shot".
Also as mention further down, waiting to get a better targeting solution and exposing myself that way is also even more a risk/reward system to consider.
Both these would be more interesting gameplay wise then "I just fire anyway, dosn't matter I will still do some damage"
Heat:
Heat should modify how fast your mech reacts to your commands. Riding the read line should slow down the crosshair and overall movement. When you run hot, you slow down in speed too.
This isn't directly a targeting modifier but would also seperate a good player from a bad one in the way that you need the experiance how hot you can run and if you have the nerves to pull it through. Also haveing the experiance to when its worth to get the slowdown seperates people.
To offset these changes you could add a mechanic that, the longer you keep your target under the crosshair, the more narrow the cone becomes, going from red (50/50 chance) to yellow and finaly green (100% hitchance)
That would offer a nice risk/reward mechanic and realy show true skilled pilots who not only have the skill to keep on target but also the nerves to wait till the ideal moment.
Overall I think that these changes would be quite nice to reduce the sniping/hiding tactic as people would risk not hitting as much or beeing exposed more to get a better shot.
Alphas have now to consider that the heat would slow them down, so reatreating would be harder and aiming too. So if you don't kill in the first strike you could be in trouble. Again a risk/reward situation.
Also TTK would increase a bit in a brawl as constant fire and theirfore heat could become a problem.
I think overall it would make for a nice risk/reward system that gives a little bit more TTK and wouldn't water down the game. A good player is still needed. Might it be that he has the experiance and nerves to decide when to fire a full alpha or wait till the target is green or be it positioning to have the time to wait to get a green fireing light.
Also teamplay could be promoted in one fireing an alpha, then the next mech comes to cover his retreat.