Hi gpolo,
Wool is a great material and with the right construction can provide some cushioning to pressure points, add to humidity control and temperature regulation, and is a less risky choice for alignment issues (because you won’t sink into it as unevenly as foam materials). It can also reduce the amount that your pressure points sink into the layers below it (which can be a plus or a minus depending on circumstances). For most people it would “soften” firm latex below it and it would “firm up” soft latex below it. In your case … it would “firm up” and may reduce the amount your shoulders can sink into the mattress because it would reduce the ability of the latex to “allow” your lighter parts to sink in more.
Of course depending on the thickness of the wool layer it would change the feel of the mattress and you would feel less of the properties of the layers below and more of the properties of the wool itself. It can also lower the resilience of the mattress surface (wool is a resilient fiber but it is less resilient than most foams). It can also even out the surface of a mattress which has some soft spots to some degree because it will increase the surface area around the pressure points which can help them sink in a little less.
Natural fibers like wool though won’t be as soft as softer foams and will compress about 30% over time (this is a natural process with fibers and not a defect) which creates a tendency to become firmer over time rather than become softer like foam layers. At first the compression may result in impressions but by sleeping on different parts of the topper over time it can even out the compression of the wool (see post #3 here). Overall and in the right circumstances they can make a very good choice and some people prefer to sleep on a thicker wool topper vs any other material. There is more about wool toppers in posts #3 and #6 here and there is also a list of good wool topper and mattress pad choices and sources in post #3 here and the links to other posts with other options. Most of them were very helpful and informative when I talked with them on the phone.
A topper with silk batting (such as the smart silk here) is another natural fiber which may be well worth considering for those who are looking for a natural fiber topper.
It seems to me that in your case a wool topper may firm up your mattress and may not be the best choice for what you are looking for (which is the reason for suggesting that you try removing your current mattress pad to see if it “allowed” your shoulders to sink in more to the latex below it). I think a thinner soft topper over firmer layers (such as what you have) and using a more resilient foam material (like shredded latex or soft solid latex) would “allow” your shoulders to sink in more and probably have the best odds of success.
If your mattress is queen size … the seven comforts topper could make a good choice (it’s currently only available in queen but this changes from time to time). They will “hold up” your hips at the same time it will slightly displace as well as compress under your shoulders and “allow” them to sink in a little more with less risk for spinal alignment.
Edit: These toppers are no longer available (see post #52 here).
The Lanoodles topper here (and see post #38 here) can also make a good choice for adding softness and pressure relief with little risk to alignment.
Phoenix