I still don't think Loghain wanted the throne for its own sake, or for the prestige of being King of Ferelden (or Regent, maintaining the fiction that his daughter still had authority as the Queen) so much as he wants the throne because he feels that he is the only person both qualified and dedicated enough to keep Ferelden an independent, isolationist nation. Loghain doesn't come off as the kind of political climber that Howe is, wanting titles for the sake of titles. It's telling that, wherever the true power may have been during his regency, he never actually named himself King or gave a hint that he was going to do so. He always referred to himself as the Regent for his daughter. It's only rumors and low-level flunkies that call him King or say he plans to take the throne. And Anora is the one who says that he may have her killed, which is hinted to be a blatant, if believable, lie told to Loghain's enemies for the sole purpose of broaching the possibility of an alliance.
The way I see it, his plan was: Preemptively destroy the most powerful detractors of his plans in the Landsmeet: Teyrn Cousland, Arl Eamon, and Arl Urien. Gain the allegience of the Circle of Magi via Uldred as a 'stick', much the same way Calenhad used them in his campaign to unite Ferelden. Eliminate a weak leader whose policies threaten to undermine Ferelden independence: ensure Cailin's death at Ostagar. Discredit the potential agents of a hated foreign power: i.e. blame the Grey Wardens for the King's death, close the borders to their reinforcements, and put a bounty on their heads to ensure survivors don't last long.
When he says at the Landsmeet that everything he has done has been to secure Ferelden's independence, he's actually not lying. Not that it excuses his actions, but his primary sins are short-sightedness, paranoia, horrendous character judgement in his associates, and a dash of hypocrisy, not hunger for power. To Loghain, the power of the throne is merely a means to an end.