Hi mreesele.
Welcome to our Mattress Forum. 
Thanks for sharing your previous configurations and some of the difficulties you’ve run into. I hope your next configuration is successful and comfortable for your wife. This thread/convo is quite long but may be useful to you - they ultimately achieved “cloud feel” with their DIY.
I looked at the Prana Lotus - they use a super plush latex - you could try super soft/super plush talalay comfort layer as opposed to just soft. It also says it includes “foam” but doesn’t specify what kind. It’s possible there’s latex foam atop a memory or gel foam of some kind which helps to create that sinking-in type feel. Wool/cotton wouldn’t be likely to “approximate” the feel she liked from that mattress but can be soft and comfortable in their own right.
NikkiTMU