I think if you want the Highland people accept you as the leader, you must put aside your broomstick and take up a sword or at least some "more royalish" weapon. Luca, Solon, Culgan, Seed, Han Cunningham and even Rowd were all using swords. Perhaps it's Highland (and Matilda) tradition? But then I'm wondering why Riou and Jowy already used such exotic weapons back in the unicorn brigade.
Howsoever, it's not necessarily Luca's sword that Jowy is using later on.
"Within the four seas, all men are brothers" Shuihu Zhuan