Why would Somalia accept French as a secondary language and/or grant her the same privileges you mention? The USSR is already heavily involved in Somalia by this point and this seems like an unnecessary move that would serve to isolate them from the source of armaments that they're accumulating for the upcoming invasion of the Ogaden.
I don't know if the Ogaden War happens ITTL but it might lead to earlier Soviet support for the Derg against Somalia which also means that Ethiopia might be better prepared but you also have the issue of the Addis Ababa-Djibouti Railroad. It might not be too much of a problem, considering it'd already been disabled for much of OTL's Ogaden War and more aid might just come through the Eritrean port of Assab - what's more disastrous is that Somalia might be able to actually take Dire Dawa, applying enough pressure on Ethiopia who's now lost her second largest air force base and an important economic center. So, Ethiopia might actually end up capitulating and conceding the Ogaden to Somalia.