The reason Gilded Shift was buffed and Verdant Radiance was adjusted is that Verdant Radiance is meant to be an early game accessory, while Gilded Shift is more late game due to the diamond requirement. So even though their values have come closer together, they're actually intended to be in different "tiers".
As for the accessory and turtle pairings, they aren't specifically designed to synergize with certain turtles, though some combinations naturally work out that way. I do plan to add more accessories in the future, and hopefully some of those will open up new synergies for the turtles that don't have as many options right now.
One reason we don't see things like jackpot chance boosting or smelting speed accessories is that I try to avoid designs that make you feel like you have to switch to a specific turtle or accessory just to perform an action on the surface. That can get frustrating over time.
Thanks a lot for the thoughtful suggestions! It's always great to hear different perspectives from players.