Here's the publisher's suggestions: Re: What we know so far
Cacao: Diamante comes with 4 additional worker tiles per player. With now 15 worker tiles per player and 30 total in a 2 player game there is no chance to keep all modules from both expansions and all elements from the base game.
Anyway the Cacao: Diamante rules give hints on how to build your custom set in the description of the "New worker tiles". Even in a 2 player game you should be able to use quite a lot of modules and elements from the base game together. You just can't have everything included, which is why we didn't call it the "Big Game" then.
Another suggestion: if you don't mind the different colors of the backs, just give both players the worker tiles of 2 colors and play a full 2 player "Big Game" with all jungle tiles included.
I haven't bought Diamante yet, so I can't comment. Though I was kinda bummed that no official variant/tweak for 2 players was included (maybe using a few extra components, or something).