I think that if you are approaching the edges of the airframe and/or pilot envelope in IMC, you shouldn't have been there in the first place.
Yes, but if we always got it right there would hardly be any accidents at all. Very few serious / fatal accidents are down to factors entirely outside the pilots control.
Recovering from unusual attitudes in IMC is a purely Instrument discipline.
It is, but many instrument pilots have failed to recover in circumstances that recovery was possible. Whether instrument training and aerobatic training would have given the pilot a greater chance I can only speculate, but I do think when the aircraft is really in an unusual attitude (I accept it should never get that far, but see above) the training an aerobatic pilots has and his stick and rudder skills might place him better.
Yeah, I know it will not happen to you, but it will happen to some hapless pilot, and it will happen time and time again. Many of those pilots will find themselves thinking why me? I always flight within my limits.
How many instrument pilots would do a good job of escaping a spin as they drop through the base?
As the CAA love saying, "safety isnt an accident" - experience protects a pilot from getting into a situation with which he or the aircraft cant cope, training expands and hones that envelope, but when experience and training fail, and the pilot has got himself into a situation with which he or the aircraft cant cope, stick rudder skills, and the ability to recognise that the aircraft is near its limits and to select the most appropriate recovery are vital skills that might just save the day.
So getting back to the original question does an IMC rating make for a safer pilot?
A safe pilot is one who always plans to operate within his and the aircrafts envelope. An IMC rating gives him the skills to operate safetly in instrument conditions. It will enable him to navigate and fly more accurately but whilst that might save him from busting airspace or getting lost ultimately I am not sure it will prevent an accident. It will enable his to deal with inadvertant IMC, but then again so will experience. There are many VMC pilots with many 1,000s of hours who have learnt that trick. However, a safer pilot is one who is the best skilled at securing a safe outcome from an in flight emergency - my point is that an emergency usually ends up with the aircraft close to the limits of its envelope some while before the impact - at that point their is no substitute for handling skills.
I rest my case, and accept you may take an alternative view, which I will read with interest.