Great find, and I don't think that any modifications at all are needed! Unless you just have a personal preference for silver buttons, in which case feel free to change them out. But you certainly don't need to -- the jacket looks fine as it is. There is no rule that all formal kilt jackets must have silver square buttons.

And a lot of formal kilt jackets I have seen have satin lapels, as well, so no worries there.

Looks great!