This variant is intended as a large board multi-move variant to test its concept if it can be made and still keep the traditional feel of chess intact without affecting the length of the game and strategy of the game too much. Only slightly modified versions of the traditional pieces are used, no new pieces. If this variant proves to be playable, then chances are balanced large multi-move variants with new pieces can be made as well.
Board setup:

Movement:
All pieces can jump over up to 2 pieces, except knights which can jump over any number of pieces.
Pawns can move up to 6 squares forward when they are on the 4th, 5th or 6th rank. Otherwise pawns can move up to 3 spaces forward.
Pawns captures by moving up to 3 squares diagonally forward.
Pawns promote on the 22th, 23rd and 24th rank.
Pawns can only be captured en passant when they move 4 or more squares forward.
Knights moves 6 squares straight and 3 to the side.
Kings can move up to 3 squares orthogonal or diagonal.
Queenside castling is made by the king moving 6 squares to the left and moving any number of rooks on the left side (that has not moved) 9 squares to the right.
Kingside castling is made by moving the king 6 squares to the right and moving any number of rooks on the right side (that has not moved) 6 squares to the left.
When castling, all squares the rooks and king is moving over must be empty (not counting rooks that are moved during the same turn).
Rooks, bishops and queens move as in traditional chess (any number of squares orthogonal and/or diagonal).
Army movement is a special multi-move that can be made by pieces standing in a 3x3 area on the board and all pieces need to be of the same piece type. Any number of pieces (above 0) can participate in the army movement. In an army movement, the pieces moving together must move the same amount of squares in the same direction (so the move needs to be legal for each piece participating). If a capture is made during army movement, then a piece is allowed to move over an enemy piece as long as the piece it jumped over was captured during the army movement (without that jump counting towards the jump over max 2 pieces/move).
If several pawns promote during the same turn in army movement, then all pawns needs to promote to the same piece.
Example:
1.A(n5)-n11 A(n20)-n14

2.A(Nt2)-q8 A(Ne22)-h17
3.A(k5)-k11

Black can capture up to 9 pieces with army movement with either his pawns or knights if he wants to. Or with fewer than all 9 pieces is also an option. Black chooses to capture with all 9 of them.
3...A(n14)xk11 4.A(Nq8)xk11

Black wants to develop his bishops with army movement and attack whites knights. However, since pieces can only jump over a maximum of 2 pieces and one of them would need to jump over 2 pawns and 2 knights, only 8 bishops can participate.
4...A(Bq23,q24, r24, p23,r23,p22,q22,r22)-h14

5.A(Bh2)-n8

Now 3 of blacks bishops can capture whites bishops since they only jump over 2 pieces.
5...A(g13,g14,h13)xm7

6.A(p4,p5,q4)xm7

6...A(Qk23)-q17
7.A(n11)-n12

Whites pawns are threatening to capture 3 queens
7...A(Qq17)xq5#

3 black queens are threatening to capture whites king. White can not capture all 3 or make a different move to escape the check, so it is a checkmate.
I think a well played game can be much longer, but this is just a miniature to illustrate how it can work.