Hi OhioMattressShopper,
Welcome to the Mattress Forum! 
Component mattress systems using latex certainly are a way to meet your requirements. Many use cotton/wool in the cover as well, and it sounds like you’re also familiar with the difference that having an organic certification can make to the overall cost of a product, even though many component systems will use the exact same latex foams as some of their organic counterparts, at a substantial savings.
Many of the members listed in post #21 here offer the exact types of “no frills” mattresses you are considering, and they are very experienced in providing the type of help and guidance on the phone that can help you make good choices. I did a quick check and many of them are also having Black Friday promotions. I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency.
If you’re attracted to the idea of building your own mattress, look at the different vendors in the component post here in the latex section. Some of these will be the same as the members I listed in my previous link, as they’ll often also sell components as well as completed mattresses. If you decide to take on the challenge then I would either use the specs (if they are available) of a mattress that you have tested and confirmed is a good match for you in terms of comfort, firmness, and PPP as a reference point or blueprint and try and “match” every layer and component in your reference mattress as closely as possible, or alternatively use a “bottom up” approach (see post #2 here). The best approach to a DIY mattress is a “spirit of adventure” where what you learn and the satisfaction that comes from the process itself is more important than any cost savings you may realize (which may or may not happen).
I’ll be interested to know what you end up deciding to pursue.
Phoenix