I think it falls down to game design philosophy here, hence why I won't enforce my view, but when faced with a choice that involves being as realistic as possible and making something fun by creating an abstract mechanic, I will usually choose the latter even though its not a natural reflex of mine. My experience is that it generally ends up making a better overall game and players tend to forgive you if it helps the product staying simple and easy to interact with.
How about a processor for each arm or a multi-brain alien? But yes, that kind of training might be a level up option, it might even be part of a feat tree.
On the other hand, I like some types of games that involve a higher level of realism and micro-management.
Yes, I guess you could say I'm coding for realism, but developing for fun. I'm starting with a set of rules which I think are realistic and then organizing them in ways that still keep the game fun. It's not easy.
I plan on making choices in the game that revolve around small details. I'm not sure how it's going to play out in the end, but that's what play-testing is for.
For example, in my game some weapons have different attack modes. A long sword can slash or pierce and a lucerne hammer can do bludgeoning or piercing damage. This means that the player selects a target and rolls his mouse over a list of attack options/ maneuvers. A tool tip or an info panel provides information and options that looks like this:
[ ] Swing: 70% chance to hit -20% damage, +10% chance to hit adjacent unit.
[ ] Thrust: 50% chance to hit, +10% damage
[ ] Bash: 60% chance to hit, +5% damage, +50% subdual damage
etc...
The player then selects the type of attack he wants to make. Of course, all of those stats are calculated by comparing weapon properties with the armor values of the target ( in addition to other modifiers - flanking, terrain, conditions, etc) .
XCOM showed you the % chance to hit someone, but that's really as far as it went. I'm taking it one step further with hopes that it won't be overwhelming to the player. Then again strategy oriented gamers don't mind complexity.