Simple and consistent, sure, but for me, whether it's meaningful depends on what kind of mental influence it had on Loki. I often find mind control in fiction to be a cheat, because it makes characters behave in ways that has nothing to do with their real personalities or beliefs or desires, and so that isn't meaningful at all. But it can be meaningful if it just heightens a drive that's already within someone or releases their inhibitions and buried impulses, e.g. Star Trek's "The Naked Time." The scene in The Avengers where the Scepter heightens the team's emotions and exacerbates their argument is a good example. So if the Scepter did the same thing to Loki, just heightened a desire was already there, then that would work for me. But that would mean it wasn't really a change in his personality, just an amplification.
And I think that fits. Loki has consistently wanted to rule because he feels insecure about his worth, because he resents being the subordinate son. After his defeat by Thor that first time, he was lost and damaged and vulnerable to anyone who offered him a feeling of power and control. I think that's enough of an explanation even without any external influence, but if the Scepter just amplified the ambition and need for approval he already had, that would still work.