Removed: 2x Triton Diver, 1x Celestial Tower, 1x Twin Soul Spirit
Added: 3x Sunsilk Faerie, 1x Laya
Having watched a few more games of Moonfassa piloting the list I felt compelled to pay a small revisit. As FTWCheese pointed out there's actually a sensible case to be made for including Sunsilk Faeries. Even without immediately gaining the buff they do provide strong synergy points with Istanu. I do like how Message in a Bottle now also doubles down as an enabler and hedges a few percentages once played. Furthermore I decided to add another potent source of single target removal in Laya as I felt the deck was lacking in this department. A big reason for why single target is good fit here but not in Mono Yellow Flyers is the scarcity of movement tricks, making for an overall less reactive gameplan, ie. your creatures having a harder time to get into position. Playing for the right setup with a proactive mindset is still a requirement, though mitigated through Last Nightmare to some extend. On the contrary in Flyers there simply is no demand because of how well the 5atk threshold scales against a lot of common stat lines when used additively. Removing 1 copy of Twin Soul Spirit gives a tad more flexibility as getting to the third lake is no longer as relevant of a requirement to absolving game states. Forgoing a copy of Celestial Tower lowers our reach by quite a bit but should ultimately be excusable since we added more charge creatures in Sunsilk Faerie.
Hopefully you found this insight into my rambling a tiny bit useful and may even apply some of the reasoning to your own deck building. Bye for now!