The big problem is the slave trade. Given that Oman was a major participant, and that slavery was one of the key drivers of their expansion, abolishing it won't be easy. And given that suppressing slavery was one of the main rationales of European penetration into Africa, Oman seems likely to be headed for a collision with powers it can not defeat, unless you change that factor instead.
(Partitioning the empire didn't help either, don't get me wrong, but keeping it united wouldn't be enough.)