If in future faction relationship change can become a thing (like previously neutral faction now hate/love each other due to player action/ major quest outcome), and Harad has multiple independent factions, then they can finally become an intersting region rather than a sideshow for westland.
Currently Harad only has 4 independent factions and 3 of them hate that one other, it's really not that fun staying in the region. Open the realtionship window and see how many factions westland has and how many harad/rhun has and you will know what I mean
Also, many of those sub-factions are interesting in lore and could provide interesting gameplay if they get to be independent factions.
Like great desert faction, they are given the lore that they trade with ppl and usually don't engage in battle themselves. This faction could become the very first faction that has no ally or enemy and treat everyone as neutral, and provide mercenaries to players. This will create the first ever hireable units that attack ANY enemies on player's command, and it would be great to have players as "mercenary lord" who go with highest bidder in a server
Others, like Umbar and Gulf and others, really have different lore and cultures. Combining all of them into a single faction just because they all serve Mordor is kinda unfair, It's like combining Angmar, Mordor and Godabad since they are all orcs serving Sauron