That would work out just fine, and I've seen it myself!! It does get darker and wetter with each layer laid. The durability is just as good as any other carnuba topper.
I didn't have any problems with layering the EX. The Trade Secret added a little more wetness to my paint. I found that 2 coats of EX and 1 coat of Trade Secret (all apllied 24 hrs. apart) gave me the best look on my black Toyota.
V, you got it right there!! That is a sweet combo. 2 coats for me is plenty. You could then do TS after, and then TS once a month to keep it looking sweet!
I love TS over EX. TS isn't the most durable wax, but it looks good. If you wax your car once a month durability shouldn't take precidence over looks. Over the winter I'll stick with Collonite, rest of the year I use TS.