Why not award bottom man 1 point any time the action goes out of bounds? Perhaps require that the action is standing. Eliminate fleeing as a penalty from bottom position.
Folkstyle Wrestling rewards control, not hanging on. If top man can't keep his opponent on the mat, does he really have enough control to deserve a reward?
It's true you'd see some absurd sprints to the edge and coaches yelling "dive out!" Things would even out quickly. There are things you can do to someone running away from you that use that momentum.
Just an idea.