Here's an idea. Use a raider, or a bullpup, or a dominion as the flag. Have them trapped at the other side constantly until a unit of the same side comes near it. Here's how the map could be layed out: (1 is side 1's units, 2 is side 2's units.)
Code:
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
X 1 2 X
X X
X 1 2 X
X 2 1 X
X 1 2 X
X X
X 1 2 X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Have an area (ill name it 'flag') around the raider owned by side 1 (its on the right side), and to make it stuck there you need this trigger:
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CONDITIONS:
Area 'flag' contains exactly 0 raider owned by side 1.
Switch 'flag captured' is cleared.
ACTIONS:
Move 'raider' at 'everywhere' owned by side 1 to 'flag'.
Preserve trigger.
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So now, if he tries to move it, itll be moved back to the area... as long as this switch 'flag captured' is cleared.
you might be asking why we have that switch. Well, here's why. When a troop from side 1 gets to his raider on the left side, we'll set the switch and the raider can move again.
If the raider is recaptured before it can get back to side1's half of the map, use this trigger:
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CONDITIONS:
Side1 owns exactly 0 raider.
switch 'flag captured' is set.
ACTIONS:
Create unit group 'flag' (this is a unit group containing a raider, it spawns at 'flag'.).
clear switch 'flag captured'.
Preserve trigger.
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and that should do it.
...but there's a flaw in these triggers. what if side 2 kills side 1's raiders while it's waiting, waiting in the 'flag' area?
There's two things we can do about this. We can have the vicinity of 'area' blocked off (use the craker crumbs to see how to keep people out of areas)
or... we can have this trigger:
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CONDITIONS:
Side1 owns 0 raider.
switch 'flag captured' is cleared.
ACTIONS:
Create unit group 'flag'.
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