you'd have to define ability. In the sense that I believe you are speaking you are relating that to proficiency in a collection of techniques or mastery of a system. You can master a system, become very effective at it (projections, throws etc as you mention)...and yet STILL lose the fight to a guy that has no formal training or "ability" whatsoever!
This is important to understand. The individual might simply have the upper hand in the situation and NEVER give you the opportunity to do anything at all. He may simply understand the environment and control the conditions. So all that practice was for nought! You can train for years and years and STILL (most likely) lose if you fail to really understand this fact.
IMO, the chances are if you are in a fight such as defined by this thread...there will be little or no chance to throw someone or break there neck. It will simply be a fight to regain control and dominance of the situation.
In most cases by the time you get to that point you are physically and emotionally spent and have very little control over most of your own faculties much less his.
Aikido training can be a good practice to augment your training for such situations, however, in my experiences and opinion....there is a reason why most professionals and people in the business of "combat" train in a much different manner than we do in aikido in most dojos.
The way i see it the word "ability" includes the profeciency in a collection of techniques as well as the warrior's way through training to be able to keep emotionally ballanced and in control of himself even if he would find himself inside the worst of circumstances because that's where it counts.The "combat" part of martial arts in my opinion is a training that helps you fight your way through a hard situation using the techniques and the calm,empty mind that we are taught in order to be able to do your best.It's not a matter of winning or losing,nothing can guarantee the outcome,is just that you win or you go down fighting!Anyway all of the above reflect the way we train at our dojo,diferent schools teach differently.It's also obvious in my opinion that people in the combat business train in a different manner because they have no interest in following aikido or any martial art as a way of life so they choose only one aspect of it...