I have a suggestion for a variant that I have been playing in person for a while now. It is simply the addition of a piece to the board, called the Spire. It is a very powerful piece worth 8 points, valued just under a Queen itself, as each player receives two it is a very dangerous world for the king. The Spire simply moves and attacks as a King and a Knight. This can become cheesy in close proximity to the king, but it is very difficult to get the valuable Spire to the opposite end of the board while your enemy may trade anything for it while not losing much even if the trade is with a Queen. It is a very good feeling moving rooks as expendable threats, the weight of adding 32 points to the board is salient. The Spire's starting position is the old Knight's position and the Knights start in front of the pawns on the edges of the board. This is an ugly setup at first, but it works as you still must activate the Knight.
Bishops are especially mean in this variant and need to be watched for early in the game as the Spire may be easily pinned if you don't know what you're doing. Castling is a much greater feat as you now need to mobilize the Spire in order to do it. The Spire may hold down massive local areas as a cleanup defense or it may be aggressive with a very odd presence on the board. Beware the slowly creeping King-walk of the Spire! as this versatile piece becomes dangerous and elusive in enemy positions. That being said, your opponent has two as well! and a simplifying trade might just occur anyway. At any rate, the board finds positions never had in classical chess notwithstanding Spire trades.
Bishops are especially mean in this variant and need to be watched for early in the game as the Spire may be easily pinned if you don't know what you're doing. Castling is a much greater feat as you now need to mobilize the Spire in order to do it. The Spire may hold down massive local areas as a cleanup defense or it may be aggressive with a very odd presence on the board. Beware the slowly creeping King-walk of the Spire! as this versatile piece becomes dangerous and elusive in enemy positions. That being said, your opponent has two as well! and a simplifying trade might just occur anyway. At any rate, the board finds positions never had in classical chess notwithstanding Spire trades.