Hey Kamnet,
It s a nice idea, i m supporting you in it !
If i may, i would advise you to directly make the "hearth of darkness" version, because as you mentioned it, the tropical basic will be the closest to the original industry...so i don t see what the interest in doing such a "long" work, for just a little difference in the end.
I understand placing more variety of industry will make more work for you, but Cindini is a map that litterally need ages to fill up, and to keep the players interested variety is the best i know. Cindini is probably not the kind of scenario where people are going to try to make all coal arrive to one power plant but more the kind of scenario where you want the most eyecandy network possible, wich variety and difficulty brings with all those different cargo.
about other newgrfs, for vehicles, i would advise you to include Ikarus bus set, the German RV set, and eventually the hungarian truck set to have more diversity. I also think that Longvehicle could be nice on Cindini (and the overtaking capacities of this last set is a must on the very long Cindini's highways). with those previous grf included you can even get ride of EGRVTS if you like. LRVS or another kind of small road vehicule set would be nice to have too for all the small delivery FIRS implies)....and small vehicles makes me think you can t go play out in the sandbox without HEQS, and Cindini is a big sandbox !
I know that s a lot of vehicule, but there is lots of highways and road in Cindini, it would be boring to always see the same vehicles
for trains, 2cc is a very good choice.
for trains stations : i wish you would add more ! I have in mind : dutch station (the original + add on), japanese station v3.5, DWE stations are the first coming to my mind.
in newobject, there is SNO = Supercheese's new object, bringing some birds (great for every harbour or even in the open sea), VAST fence can be usefull too
and what about buildings ? are you planning to stay with the originals ones

? swedish house mixed with the japan set looks great, there is not huge skycrapers everywhere cause they are limited in the japan set and swedish house don t bring big skycrapers, i guess more building set would even be cooler but i don t know wich (please avoid TTRS and north american, we can t see the streets with those grf)
I m also hoping you plan to select a new road grf, and a compatible bridge set
And btw if you need help for building the scenario, advice or just chatting about your project i m here, i believe i could bring you experience from a big multiplayer game i had on Cindini 2.0.
Edit : also do you maybe thought to add a script ? like neighboors are important ,i t could make sure not every town will grow as big as Capitola....and will make it quite challenging to meet the demand to make grow those huge cities

....it s just an idea, it s stilll maybe need to be tried first...adding script to this scenario might mess things up.