Hi Fluffhead,
In theory … this seems that it could work as per our previous discussions. In practice however your experience may be different because of the many variables in sleeping positions and each person’s different sensitivities to both pressure issues and alignment. Layer thickness can play just as big a role as layer softness and since this is an untested layering for you … your experience may vary from theory. The basis for the possibility is that a 2" layer seems to be in the range of overall thickness that both you and your wife can build a layering scheme that would work well for both of you. The “risk” for you is that the top layer isn’t pressure relieving enough even though your experience seems to indicate that this would be OK. The “risk” for your wife would be that the top layer wouldn’t be soft enough for her lighter weight (even though the thickness is typical for back sleeping). Based on your experiences though … the “odds” say that it would likely be OK although I would put being “right” over the small difference in cost which spread out over the life of a mattress will not be that significant. Of course I wouldn’t bet my house on it … but I’d throw $5 into the pot 
I also think that a non quilted cover gives you options that quilting built into the cover doesn’t offer … although there are many who hold different opinions about this (involves different fire retardant methods and introduces variables that are slightly different from what may have been tested etc.).
When it comes down to the final details or “exact” ILD’s bear in mind that there is no such thing as a layer that is “exactly” a certain ILD and that a difference of 4 or less is not really noticeable for most people. With details that are that “fine” I recommend that people go with their instincts or “gut feeling” based on what you have tested rather than a recommendation from someone who has never “felt” what they felt. In general you will have a sense once you’ve tested various layerings of the ones that were close to the edge of either pressure relief or alignment and whether it’s “safe” to adjust a little bit in one direction or another for either pressure relief or alignment. The 3" layer may be safer (because you’ve tested it). The 2" layer may be more “accurate” but a little riskier.
I would also take into account any recommendations or comments from the actual outlet you plan to purchase from as they all have a lot of experience with a wide variety of different people using the specific materials and ILD’s that they generally use or have available (although most can custom order something different) in combination with the layering patterns that they are familiar with. In the end … while it always desirable to get it right the first time … it’s also important to have the ability to “fix” any mistakes because the process of choosing a mattress is never an exact science … even though testing and some careful research can put the odds much more in your favor. sleeping experience over time can be different from time spent in a showroom. Careful testing can make it very likely that you will make the best choices the first time but there are always exceptions and it’s a good idea to be prepared for this just in case and “build it in” to your purchase choices. Layer exchanges, refund policies, or a local manufacturer who will change out a layer or make other adjustments are all ways that mistakes can be fixed with little risk or expense (although there will usually be some).
In terms of heat … layers that are firmer (in relationship to a particular weight) tend to “wrap you up” a little less and are usually less of a heat problem. Talalay latex is also the most breathable foam so here too the heat issue is reduced or eliminated for most people. Because of the breathability of wool, this can help with heat issues for those who are very sensitive or have a “hot engine” inside them. Mattress pads or protectors, sheets, and bedding can all make a significant difference to heat issues without having to adjust the mattress itself.
100% Talalay is more springy or elastic than blended but with a single layer it wouldn’t be noticeable for most people. With a whole mattress however the difference would be more noticeable. This could be a positive or negativ depending on the preference of an individual and on how they interact with the mattress. What can be “springy” for on person can feel “bouncy” for another or even “dead” to another depending on perception, what they’re used to, and on different body shapes and weights. The 100% natural is a denser material as well and not quite as “stiff” as blended which also means that there is a greater tendency to sink in a little deeper. Pure Latex Bliss is a mattress brand owned by the largest manufacturer of Talalay in North America and they have a blog which has an article here which describes the difference from their perspective. Note that what they call “natural” is blended and “all natural” is their 100% natural Talalay.
Mattress pads or protectors are a series of tradeoffs. The “waterproof” versions that have a membrane (like gore-tex_ which allows water vapor through but blocks water are less breathable than those that are made of wool which are water resistant but far more breathable. For most people the thinner membrane type are a good compromise but for those who want the most breathability then a water resistant protector or pad is the way to go. More in this thread here (post #5 in particular with actual temperature measurements), and post #2 here, about the tradeoffs involved. A forum search on “protectors” (without the quotes) will bring up more.
Hope this helps
Phoenix
PS: I deleted the other post which was a duplicate and somehow created a new thread. Hope that’s OK