Economics and good governance are not a sufficient justification for the breaking up of a state. Somaliland's bid for independence is basically a Trojan horse for the collapse of whatever remains of pre 1991 Somalia.
Somaliland meets every condition the requirements of a state in international law. None of the other regions in Somalia can meet it if they decided to leave. And if they really wanted to declare independence they would have done it by now. That reason isn't based in reality.
The state as a person of international law should possess the following qualifications: (a) a permanent population; (b) a defined territory; (c) government; and (d) capacity to enter into relations with the other states.
I think the best rebuttal to your claim that Somaliland did not become a part of Somalia is the fact that Somaliland would be automatically recognized by the entire world if the parliament of Somalia voted for it. If Jawaari brought a motion for recognizing Somaliland's independence and it passed, the whole world would follow a day later. That is the clearest proof of what entity was subsumed and which entity did the subsuming.
That's actually not true. The process will be first having talks between the Republic of Somaliland and Federal Republic of Somalia to discuss border policies, visas, economic cooperation etc. and then have a referendum monitored by the United Nations in Somaliland. If the people of Somaliland vote for independence, the United Nations will then accept them as a member state. The parliament of Somalia has no say in this process at all.
That's how it was done for Eritrea, South Sudan and other recently independent countries.