You might be right about this.Ethiopian Navy was plainly impossible until approximately 1925, due problems with transportation from inland (which is a must to build ports). Roads must be built first. In practice, Ethiopian can hope at best case for torpedo boats and may be some obsolete Japanese destroyers by 1935. In particular, Ethiopia may hope to buy some of Harusame-class destroyers which Japanese scrapped in 1924-1926 IOTL.
As i understand, H.S. I ascension from regent to emperor was a formality. He had enough of absolutist power from 1916 already to enact severe reforms, and i see no significant speedup in reforms after 1930 IOTL.
With a professional well-trained and well-equipped army under his command, HS could've instituted more radical reforms without the nobility being able to resist. The reason reforms came so slowly was due to Haile Selassie's careful maneuvering to prevent himself from being removed by the influential reactionary nobility - I would say HS would be able to implement more reforms and faster with an army that could destroy the nobility's own armies and either force the nobles to submit or get rid of them.