As someone who has played a LOT of SRB2, as well as several modded characters, I have a few thoughts that might help make this mod truly shine:
1. Make the Crash Dash a toggle. Having to hold Custom Action 2 to move faster feels clunky, and generally unsatisfying in this game. Having it be a toggle would feel MUCH better.
2. Allow the Death Tornado Spin to be used on the Ground. As someone who played A LOT of Crash 2 and 3, it feels very wrong that I can use the Death Tornado Spin in the air, but not on the ground to make my attack longer. (I often get hit because of this, and it feels a little cheap, I know it's a skill issue, but damn you muscle memory!)
3. Crash is unable to do Multiplayer Special Stage 1 due to being too big to fit into the pillars. This makes playing Solo on a Server simply exhausting and making it worthless to get Emerald Tokens until after the first emerald.
4. The inconsistency with the sprites. The finished sprites look amazing, however, there are several that look more like a general outline and should hopefully be updated when possible. I am sure the mod dev has been made aware of this however, but I'll through in a few small notes for what I think they could do: For the Spin, add trail lines to show that Crash is spinning quite fast. It helps keep the movement looking less like he's just T-Posing, and more like the original.
5. When the sprites ARE done, I think Crash could easily benefit from the Secondary Custom Color that say, Mario and Luigi have for his pants and yellow fur. Helps keep Color looking nice and keeps from certain colors from bleeding into each other.
6. Maybe incorporate the Elemental Shields from Sonic into Crash, A way you could do this is by using the Elemental Masks from Wrath of Cortex, or by changing the color of Aku Aku, like he changes to the clear white in those Night Stages. For what the shields do I also have a few ideas:
Attraction (Magnet) Shield: Crash's Spin can now pull in enemies. (You could use Apo Apo from CTR:NF)
Force Shield: Gives Crash the Super Charged Body Slam.
Armageddon Shield: Crash's Belly Flop triggers the shield. (Could be Uka Uka, which would be really funny, otherwise, you could make Aku Aku just spin around Crash really fast)
Whirlwind Shield: Crash's Death Tornado Spin now gives him height when used in the air. Not much, but it should be noticeable that he's going up instead of maintaining height.
Elemental Shield: Crash gains the Super Slide from the GBA games, letting his Slide go much further and faster. (Leaving Fire particles behind him would be an interesting touch)
Flame Shield: The Death Tornado Spin now gives Crash a large amount of horizontal movement and speed, like Sonic's Dash (Easily using Py-Ro)
Bubble Shield: Crash's Belly Flop now works like Big's attack in Sonic Heroes, bouncing him back up when used. (I know it's not exactly a Crash thing, but I think it would be a cool little reference.)
Lightning Shield: Crash's Double Jump now goes much higher.
Just think it could be cool to have a blend of Sonic and Crash would be an interesting way to add more to the character. Feel like bringing Crash into the World of Sonic instead of overwriting it.
All and all, very excited to see where this mod goes!