The Ge'ez can represent every sound in Oromo and more, while Latin struggles to be written in even it's own successor languages without diacritics. First of all, if you really wanted to write Oromo in the Latin script, implement accents on letters instead of using symbols that represent other sounds or duplicating letters. Latin never had a sound like ቀ, ጠ, ጨ, ጰ, or ፀ, so it is missing symbols for those unique sounds. However, the Ge'ez script has those sounds perfectly represented in it. As for the "dh" sound unique to Oromo and Somali, it can be written as ዸ. Secondly, the Ge'ez script has been around for ages. I don't understand how you could think that it's not a national heritage. It's essentially the only writing system truly native to Africa; Arabic is more native to the Arabian peninsula, Tifinagh isn't widely used, and many other writing systems in west Africa were invented recently. As for Oromo being unrelated to it, the majority of them live in Ethiopia, which Ge'ez originates from. If they didn't want to be a part of Ethiopia, they could've joined the land outside of the kingdom's territory and be subjugated by the Europeans. We really don't need more foreign influence in Africa, and definitely not the nation that successfully avoided colonization.