In 1444 India had relatively little interaction with England. By your logic the mechanism by which events in India affected Europe was through the Middle East. What is revisionist then in saying: If event X or Y would have happened in India, Western Africa could have been directly affected by Indian politics? In fact on this very forum we have a couple of Indian WC threads. These are ahistoric, but not because the players gamed EU4 but because it is a sandbox game starting in 1444.
Really the question you arise here is whether we force actual (constructed and interpreted) history in EU4 or allow anything to happen but make it possible to get to the same situation in 1821 as it was in our historical timeline - depending on the decisions made (and those of the AI of course).
EDIT: sorry, I seem to be stalking this thread right now. I am heavily procrastinating, you know.
In 1444 the central nodes of world interaction were the Ottoman empire and the declining Timurids. These two empires provided the dominant linkages between India and Europe. Up until about 1470 (give or take) Europe is not central to the international state-state interaction network.
I have no problem with players doing ahistorical things like forming pan-Indian empires from OPMs (the Mughals did it, the OE did similar magnitude stuff in the 150 years before the game's start). My point is that if we want good historical strategy, where the player has to contend with something like the strategic calculus that states faced in the time period, then yes getting Africa "right" is a lower priority (which is not to say Pdox is correct in doubling down on the new world from this metric, if creating accurate strategic setups were the only concerns we'd have refined the hordes as our first DLC, and then gone on to Asia which has been woefully neglected given how important India and China were to world history).
What I have a problem with is people blithly dismissing the fact that new tags come with prices:
1. The game does run slower. New tags are some of the most computationally expensive things to do with the game. Tag bloat for no reason should hence be a priori avoided.
2. Africa loses some of its strategic uniqueness. Historically, Africa was not a hyperconnected region with well defined states that continuously transitioned from one state to the next. It is frankly "Eurocentric" that we open up African wastelands - areas that were treated as such by the major African powers, just because Europe lacks wastelands. An African DLC should strive to introduce actual African mechanics - better modeling of the gunpowder empires, the effects of the Atlantic and Indian slave trade, perhaps the Bantu migration, or having some sort of "unorganized" natives interaction mechanics (e.g. African states can spend MP to integrate natives from uncolonized provinces). All of these are actual mechanics that existed in the period and would better reflect the differences that Africa faced compared to central Asian gunpowder empires (like the Mughals) or India (e.g. Mysore).
3. The AI gets horridly flummoxed when we put in land, but then try to make it undesirable to interact with in the normal ways. The AI is already terrible at managing wars in Africa. This tends not to show up to much because most players, by the time they start seriously contesting Africa, are so powerful an AI nerfing itself to cross the high attrition area doesn't register. But the more places this occurs, the weaker the AI will be.
At the end of the day we come down to the simple question, could any army have marched from a currently existing state, carried/foraged enough calories to emerge in fit condition to fight (e.g. with enough upper body muscle mass to wield period weapons), found enough water to support their transit, and then been able to return after the conquest. I have yet to hear any sort of evidence that answers this question with real evidence. Will your soldiers subsist off even light jungle fare? I know of nothing that is edible for humans that exists in a jungle to supply a few thousand men marching with a mile of frontage (very generous estimate there). Will they carry there own water (that is a huge calorie burden) or drink from the rivers & ponds (high temperatures mean a LOT of pathogens who like human body temperature will be present)? Either option is tough. And so on and so forth.
Looking at the region
right now I see no way to move 5,000 men in good order by living off the land over any of the areas people are proposing. Until there is an answer of how this would actually occur, I think it is far, far safer to leave these areas isolated out of respect for their actual history rather than trying to shoehorn them into ill-fitting European models of organized states and accessible terrain.