Hi Khetre.
Welcome to our Mattress Forum! 
With the 6" Lucid, temperature may be more of an issue for you, but again this will depend entirely on your tolerance. You are correct that the upper layers of the mattress are the most significant when it comes to temperature and moisture regulation and that Latex, in general, is also not only the most durable but the most breathable and “temperature neutral” of all the different types of foam materials but the firmness of a mattress and how much you sink into it can also affect sleeping temperature as well. While it’s also not always possible to track down temperature regulation issues for any particular person on a specific mattress because there are so many variables involved (including your room temperature and humidity, your sheets and bedding and bedclothes, your mattress protector or any mattress pads you are using, and where you are in the “oven to iceberg” range) and some people can sleep warmer on mattresses that most people are generally fine with … there is more about temperature regulation issues (at least to the degree possible for a specific mattress) in post #2 here and the posts it links to that may be helpful.
If you like the feel of latex and are concerned with temperature regulation then the 10" Lucid “Latex” Hybrid Mattress would be an all in one and have the advantage that you won’t need a topper. This mattress is using 1" Dunlop, but there isn’t complete information about the blend or certification information about this foam. There is a 7" polyfoam core beneath it but the density is unknown, so this is not an all-latex mattress. A forum search on Lucid (you can just click the link) will bring up comments and feedback about them. I know that you are looking to get only 2 to 4 years useful life for your mattress and I’d just want to make sure that you are aware that Lucid is from China, and you can see in post #6 here more info about mattresses imported from Asia or China which may have been compressed for long periods of time in either shipping or storage before being purchased, which in my opinion makes this a more risky purchase.
At your BMI and with the durability expectations you mentioned you seem to be looking in the right direction, but I would also consider guided DIY option which would be more along the lines of mattress/topper version that you are considering, although I don’t recommend this option without the guidance of an experienced and knowledgeable retailer/manufacturer. For example, you could purchase here a 7" TwinXL poly layer of 1.9lbs (for $165)) then add a latex topper of your choice and a mattress cover.
Just keep in mind that while we can certainly help with “how” to choose … it’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP (Posture and alignment, Pressure relief, and your own Personal preferences) or how a mattress will “feel” to you or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
Nobody can speak as to how any specific mattress will “feel” for someone else or whether it will be a good “match” for you, but if after you find out the specifics of each of the options you are considering in terms of the information listed here so you can compare the quality of the materials and components to the durability guidelines here just make sure that before making any purchase you are OK with some of the risks involved that come with some of the lower quality options you are considering.
As far as powerbase suitability for the specific mattresses you are considering, this would be a question to ask the manufacturer/retailer themselves, but in general terms … foam materials such as latex, memory foam, or polyfoam along with most pocket coils are “bendable” and flexible enough to use with an adjustable bed and all the options and the mattress thickness you are considering would work well with a powerbase.
You can see some of the threads where Lucid was discussed here connected with washable cover issues that consumers experienced. As far as mattress protectors choices, there are many … membrane type … the wool type … or the cotton type. The tradeoffs involved are between how waterproof they are … how breathable they are … how much they will affect the feel of your mattress, the importance of natural materials, and of course cost. There is more about the choices and tradeoffs involved and the amount of “protection” that may be important in post #2 here and in post #5 here.
I hope this gives you enough information to help with your decision.
Phoenix