Your last argument works in reverse too, as it's advantageous to balance our factions and play them against each other rather than empowering one at th cost of another (with the understanding that Susenyos's presented choices will always favor the miltiary).
As for the rest, not opposing the Harari could embolden the Sultan to mount an offensive against us, as we're not protecting our borders. The Maya, meanwhile, might cost us some taxes, but they're not going to escalate to a point we can't handle.
The Wej campaign is achieving that by reaching out an olive branch to the merchants even as it simultaneously helps to satisfy the army and earn the respect of the powerful tribes. Recall that, although we were not the
worst candidate in their eyes, the merchants were nevertheless not keen on our accession as they're not liking military adventures that risk blowing up trade routes nor our inclinations towards our heterodox practices. This path finds a way to satisfy and gain the respect of our key stakeholders in the army and ensuring tribal peace while also soothing the outraged demands of our merchants for justice from these raids, all while we're going to be supporting the bureaucrats with our choice of Lemuel for Bitwoded. I find that to strike an admirable balance in terms of bringing in new factions even while giving a gift to sate the ones responsible for gaining us our throne to ensure their continued backing, and those particular newcomers have much to give us with our currently sagging administration and income. On the other hand, the church
hated us. We were their single least favorite candidate, the one that they tried to avoid at all costs by backing literally every other candidate and injecting themselves into those politics. Why should we rush to shower them with favor and a quick response before we've even rewarded our actual supporters? There's not anything special that we're looking from the church at the moment, not like the income we really need to have coming in which is worth coming to terms with the merchants for.
The Sultan by himself is weaker than his emirs, as Telamon states on page 5 here. Actually, looking up the history of the Sultanate of Adal on Wikipedia, it seems that in this time period it's to the extent that the Sultan is pretty much a puppet of his emirs by the current year of 1478.
Emir Laday Usman subsequently marched to Dakkar and seized power in 1471. However, Usman did not dismiss the Sultan from office, but instead gave him a ceremonial position while retaining the real power for himself. Adal now came under the leadership of a powerful Emir who governed from the palace of a nominal Sultan.
[41] Mohammad Hassan states Adal Sultans began losing control of the state to Harar's aristocracy, the Harari and Harla people.
[42]
As such he seems most unlikely to undertake independent action outside of what will benefit his Emirs... and why would the rest of the emirs controlling the Sultan want to empower Harar's position by expanding it against us? However, that calculation changes if we start going on a conquering spree next door; none of them want to be conquered and lorded over by an infidel emperor, and neither will they take kindly to us blowing up their local trade.
And again, matters
can get quite bad if tribes (who again are one of the largest powerholders right now) sense weakness from us not bothering to respond to these tribes not only standing down from their duty but in fact turning their arms against us while our income is really hurting. We are not far off from the age of the Oromo migrations, where pastoralists from the south started with raids, found weakness as they encountered Adal and Ethiopia distracted by warring with each other, and swept up to settle and conquer wherever they could, picking up power and momentum as they won more and more and gained horses and serfs from the north. These migrations caused massive chaos and realignment in the region, and the collapse of many states. It's a bad idea to just ignore tribal raiding and say oh no big deal, one tribe might not be but if they are making off like bandits then there's a great many others who could start getting ideas and it can get quite a lot to handle while simultaneously engaged at another front.