Is there a user constructed version of the pain field?

Yes, there is the Skywall Shield Emitter. It looks like this:

The color depends on the faction which built it. This is a Vanu one, so it's purple.

When an enemy soldier comes into contact with them, they will set them on fire and do damage over time. That DOT will persist for a while even after they leave the area. If they leave immediately they might survive with HP in the red zone.

They form a mushroom-shaped cupola 15m over the generator. The intended purpose is to prevent light assaults from flying in and to counter galaxy drops, so the enemy is forced to attack on a ground route. However, some players will try to place them in ditches (like here) so even ground-based attackers have no other choice than walking through them.