Imagine a super giant scale as following:

More team members on the pane the heavier on that side, and therefore the heavier pane move down but the pane at the other side move up. (Winning condition) The pane first touches the ground would cause the destruction of the other pane. The losing members would of course fall to their death!
A magic "switch" at a remote location. This switch (on/off) which have an opposite effect to the scale. Turning the "switch" on would have the following effect: The heavier pane would go up but the lighter pane would go down. Turning the "switch" off would makes the scale behaves normally.
Here are the strategic elements of this map
1. More members on a pane would make the pane heavier and therefore move down, but the pane of the other side move up.
2. Guarding the switch would also very important for winning the match.
3. Players on each pane could shoot at enemies on the other pane when two panes are close to leveling position
4. Panes always move up/down at a constant speed (+x m/s or -x m/s). Just like other maps where more members push the kart would not make it go any faster (constant speed), same idea.
5. Both panes should be big enough for full team to maneuver (evading bullets, rockets, arrows)
6. Members can travel to the pane of the opposite side. This gives great advantages for pyros and spies. Of course member who travel to the pane of the other side would contribute +1 weight to the opposing pane.
7. Engineers can build sentry guns on their pane only (cannot build sentry on the pane of the opposing team). A sentry gun would contribute +1 weight on their own pane (regardless of the level of the sentry). Dispensers and teleporters would *not* contribute any weight.
8. There are several interconnected large tunnels/shortcuts that allows players to travel to the both panes or to the remote switch.
9. Players (on each pane) cannot see/reach each other in the first 2 minutes of the match even if both panes are close to level position.
Basic Tactic
A team would decide to split into two groups, the defending group and the attacking group. The defending group would sit on the pane and hope the other team has less members on their pane. The attacking team would go through several "short cuts" to areas where they can shoot at the enemies at their own pane. Killing enemies at their pane would make enemy's pane lighter.
The biggest differences between my idea and other conventional maps:
1. A team can directly affect, and have an positive or opposite effect the advancement of the opposing team. Other maps would not let you undo opposing team captured points or pulling back/pushing the enemy karts directly.
2. With the introduction of the switch(on/off) and the dynamic nature of both panes, this let even a small group of skills players to out-play a large team of un-organized players.