I find that just about any jacket is uncomfortable in hot, humid weather if you are sitting still. So long as you are moving 25 mph or more and your jacket has decent ventilation, you are okay. 40 mph+ and you are actually comfortable. That is, unless it is 100* or more out, in which case no amount of cooling works. On those days I either suck it up and suffer or just avoid riding as much as possible. For my SA trip, I have no hard schedule so I can sit out a few intolerable days if need be.

That said, I like your suggestion. I have considered just scrapping the Latitude and buying a Traverse or something and then wearing body armor underneath. If it is super hot, the body armor is fine sans jacket. I've seen/read guys that do this in Vietnam, etc.---countries that are notoriously hot and humid.

Ecuador can be hot, but the elevation helps offset that. At low elevation its coast is a lot like the coast of southern California, namely, desert coastal wherein the dry heat and cool ocean water makes for temperate Mediterranean climates. I did ride through the orient (i.e. east) for a day and it was hot and humid. Not the most enjoyable ride, but motion and venting kept it manageable.

In the end, there is no single jacket that will work for high altitude and cold climates as well as hot humid jungle climates. I figure the best option is to get the most versatile jacket and then supplement with other gear, water, etc.

On that note, I will be taking my Shoei Hornet 2 helmet rather than my Shoei 1100, even though my 1100 is a much better helmet---quieter, better protection, more vents, etc. This is because with the Hornet (a DS helmet) I can ride with the visor open and goggles on, which is much cooler than the street helmet in any condition. Just something to consider as well. For me, the comfort of my head is of primary concern, then I care about my hands, then torso, then arms, then feet, then legs, in that order. Your priorities may vary.