That is indeed a nice thought, though in this case i think it works both ways as a gift, kinda like buying you wife a lacey black neglige.
I think this hilt looks fine, certainly better than the original, though you should show it in the sheath because the hilt really needs to look best with that as together they are the outer wear clothing of the keris and that will tell us more as to the "correctness" of your choice.
I wouldn't personally change out the mendak just to put some fancy bejewelled one there as you don't necessarily want to out shine the keris itself with it's fittings. You might want to consider the keris itself first, the level of quality that it is, the level of wealth that an owner of such a keris might have, before you make any changes.
