Cross-Hairs

Definition:  A piece is on an enemy line if it belongs to a line of adjacent pieces (of either color or type) between two enemy pieces. A line similarly includes any sequence of adjacent edge cells.

RULES
1.  On each turn, each player must drop a friendly soldier on an empty cell adjacent to any stone AND then, optionally, move any soldier to an adjacent empty cell which is adjacent to any other piece. After each drop and after each move:
1.1   Any enemy soldier not on the edge and belonging to *two* enemy lines is replaced by a friendly King;
1.2   Any enemy soldier on the edge belonging to *one* enemy line is replaced by a friendly King;
1.3   This replacement only happens if the dropped/moved piece participates in one of those enemy lines;
1.4   Kings are never replaced and do not move.
2.  When all cells are occupied, the player with more Kings wins.

 abcdefghijklmnopq
     . . . . .     1
    . . . . . .    2
   . . . . . . .   3
  . . . . . . . .  4
 . . . . . . . . . 5
  . . . . . . . .  6
   . . . . . . .   7
    . . . . . .    8
     . . . . .     9
 abcdefghijklmnopq

Sample Game:

      ooo         xxx    
   ----------------------
1.  i5  --      j4  --    
2.  k3  --      g5  j4h4  
3.  f6  k3i3    k5  h4j4  
4.  e5  i3h4:   e7  --    
5.  l4  h4i3    m5  j4k3  
6.  l2  l4m3    d4  k3l4  
7.  n6  m3n4    c5  e7g7:
8.  l6  l2k3:   h6  l4j4:
9.  a5: f6e7    o7  h6j6  
10  h6: h6i6    h8  j6k7  
11. b4  e7d6:   j6: o7p6
12. q5  n6o7:   c7  g7e7
13. d8  a5b6:   a5  d4c3:
14. d2: d6f6    e9::j6h6
15. g9: d2e3    d6  e7g7:
16. e7  e3f4:   f8: h8i9:
17. h8  f4d4:   j8: h6j6
18. m7  q5o5    m3  i9k9
19. l2  d4f4    n6  m3o3:
20. n2  o5p4:   n8  k7l8:
21. g3  p4o5    q5: q5p4
22. q5: n2m1    h2  n8m9  
23. f2  i3j2    n2: n2m3
24. i1: n4l4    k1 m3n2:
25. n8: i1g1     resign

abcdefghijklmnopq  
    . o . @ #     1
   . o @ o o @    2
  @ . o . o . @   3
 # . o . @ o . @  4
@ @ # @ # @ @ o # 5
 # @ # . x # x @  6
  @ # @ # . # #   7
   # x # x x o    8
    @ # . x x     9
abcdefghijklmnopq

One possible variant would remove the edge rule, turning the board into a hex-torus. This has pros and cons, it simplifies the game but at the cost of some clarity (the board topology would become harder to grasp).