Welcome, Producer Matsui. よろしくお願いいたします。
I have two suggestions: one specific and one over broad context.
-- As a specific point, the Alexandrite cost of Mythic Weapons is too high. Downright, totally, utterly, completely, unjustifiably, too high. I love the concept (mastering every facet of Aht Urhgan to acquire its true treasures) but the alexandrite cost is needlessly outrageous, to the point of being called insane. Particularly considering that most mythic weapons just flat-out aren't any good. As you are seeking suggestions to fix problems instead of blatant ramblings and whinings of 'what's wrong with the game' (which the forum-dabbling player base is very good at, as I'm sure you've noticed...), I simply suggest lowering the cost to better match the amount of alexandrite in circulation. I see no need to adjust the structural integrity of the Aht Urhgan endgame events that produce Alexandrite if the base amount needed for the mythic weapons is adjusted to a more reasonable value.
-- As a broader point, please understand that the intentions of you, and the development team, are not the carved-in-stone absolute truths that we need to play the game by. Many comments made by the development team and passed down through their lovable forum minions (Camate, Okipuit, etc.) are inaccurate, sometimes to the point of insulting the player base, and on occasion are flat-out wrong (see: Flame Geode/Weather discussion, Treasure Hunter+ for Pet gear discussion). In a game of this size and magnitude, the opinions and intentions of the development team with regard to in-game content are second to the opinions and interpreted intentions of the player base, and sometimes the responses from the development team really feel like they're trying to control how we play the game. It's ridiculous and insulting at times. Put the words, observations, and tested results of the players before the "it-looks-good-on-paper-so-it-must-work"-esque observations of the development team.
Thank you for your time. I am anxious to see what your new leadership will bring to the future of the game.