This will be the first US ambassador in the 23 years since closing the US embassy. It shows a great deal of respect and will instantly provide new methods of communications. With both sides believing in an opportunity for progress, there is new hope for improved relations. A new start always shows hope for new opportunities.
Without dialogue, there can be no good relationship between countries. The new United States ambassador to Somalia will improve relations between the two countries by filling a position that has been non-extant for two decades. Somalia will take the appointment as a sign that the US has new faith in Somalia's government. The United States will have a new diplomatic commitment. Dialogue will be established as the countries begin to work together and build a relationship.
It doesn't matter if the Dali Lama is the ambassador to Somalia, that country is going to be a backwoods pit of piracy, murder, and gang violence for the foreseeable future. The country is so incredibly unstable and has such a massive population of just flat out bad people that it isn't going to improve with a new ambassador from the US. The only way relations with Somalia will ever improve is if a legitimate government takes root.
While I'm sure they will nominate an excellent candidate, but I don't believe much can be done because of all the turmoil in Somalia. The country is in chaos and I don't believe a single person can change an entire countries relationship with the United States. The plight of Somalia is so much deeper than one person could presumably take on while not receiving much power to do anything from the current administration.