Champion and Wizard sound quite interesting, and I think interesting mid to low value pieces are lacking
The Wazir+Xiangqi horse is probably my favorite out of all these. Maybe call it the Xiangqi Marcher. Very interesting low-ish value piece.
The Queen and Wildebeest piece aka "Death, destroyer of Worlds", (and similar versions like Queen+KnightRider+CamelRider or Amazon+AlibabaRider+Grasshopper) has been suggested many times and is unanimously agreed to be so powerful it doesn't matter, and all versions of it are either stupidly powerful or barely better than the amazon, which is already powerful enough.
Crowned Rook is actually in a group of variant pieces, collectively called "crowned pieces." A crowned piece is simply the moves of 1 piece + the moves of a king. So a crowned bishop would move any amount diagonally or one square orthogonally, and a general is a crowned knight.
I realized that it would be too hard to chess.com create the option of creating custom fairy chess pieces. so theres my suggestions of fairy pieces that i think chess.com should add, and i dont think this would be too hard to code
Champion:
this piece combines wazir and alibaba, this piece is from Omega Chess (https://en.wikipedia.org/wiki/Omega_Chess)
Description on chess.com: "combines alibaba and wazir"
Notation: Σ
Wizard:
this pieces combines ferz and camel, its allso from omega chess (https://en.wikipedia.org/wiki/Omega_Chess)
description on chess.com: "combines camel and ferz"
notation: Π
Crowned Rook:
combines Rook and ferz
description on chess.com "combines rook and ferz"
notation: μ
Dragon Wazir:
it combines wazir and xiangqi horse
description on chess.com "combines wazir and xiangqi horse"
notation: Γ
Actress:
it combines Queen and Wildbeest
description on chess.com "combines queen and wildbeest"
notation: Φ