I hope this isn't too many suggestions I'm about to make. You DID ask for them, but I also feel like throwing a bunch of ideas at you all at once could come across as rude or demanding. So...I'm going to do it anyway but preface it with this short blurb. That makes it perfectly OK, right?
Arctic Diving Gear + Lava Waders + Obsidian Rose = Thermal Diving Gear
Combining the items that protect against liquids of extreme heat and cold into one just seems reasonable to me. The boots always struck me as more speed and height oriented. Speaking of which...
Lightning Boots + Frog Leg + Lucky Horseshoe = Skyware Boots
Lightning instead of frostspark because it fits the sky theme and I always thought the ice bonuses felt better on the diving gear anyway. Maybe that's just me.
Black Belt + Gi = Martial Artist Outfit
This would then replace the Black Belt in making the Master Ninja Gear. Mostly this is just to get the Gi into that combination, since it seems like it would slot in nicely and doesn't really work anywhere else in my experience.
Magic Cuffs + Mana Flower = Flower Cuffs
Flower Cuffs + Celestial Emblem = Celestial Cuffs
The Celestial Emblem struck me as underwhelming compared to the other emblem accessories. The lava glove adds knockback from the titan glove, speed from the feral claws, and fire from the magma stone. It doesn't strike me as unreasonable to give the other emblem accessories similar treatment.
Magic Quiver + Endless Quiver = Archer Supplies
Rifle Scope + Endless Musket Pouch = Gunner Supplies
Avenger Emblem + Archer Supplies + Gunner Supplies = Artillery Emblem
The ranged emblem accessory only working for guns struck me as a bit odd, as did the fact that the destroyer emblem it used really wasn't ranged-focused at all. Instead, my idea for this would be to grant a larger change to avoid ammo use with the "supplies" accessories, then make the arrow and gun bonuses of the quiver and scope apply to all ranged weapons with the emblem.
Avenger Emblem + Shark Tooth Necklace = Shark Tooth Emblem
Shark Tooth Emblem + Eye of the Golem = Destroyer Emblem
Since I took the Destroyer Emblem out of the ranged accessory, I figured it might as well be re-imagined as a general damage emblem. The shark tooth necklace has an interesting effect and isn't crafted into anything else, so this struck me as a reasonable place to put it.
Avenger Emblem + Pygmy Necklace = Tiki Necklace
Tiki Necklace + Papyrus Scarab = Bewitching Necklace
Summoners don't even HAVE an emblem item. The summoner emblem can be made into the avenger emblem, but then that can't be made back into a summoner item like the other damage types get.
Well, that's all the random ideas I've had while playing 1.3. Feel free to ignore some or all of them, since this is of course your mod. Really these are all just things I wanted while playing and would make myself if not for my complete lack of any and all ability to code. Or make sprites. Regardless, the stuff already IN the mod looks awesome and I'll definitely be using it as soon as I figure out how using mods with Terraria even works.