Just a thought sue, but isnt that screw jack gonna take quite a bit of leverage to lift a camper. It seems like it would be great to set something on, but a biotch to lift something. I know that construction scaffolding often uses bases like those screw jacks to adjust the scaffolding. If there is any weight on it, you cant lift it to save your life.

I would personally steer away from those. Bottle jacks are far stronger due to the assistance of hydaulics.
If it were me I would use a bottle jack to get it level, then use wood or really sturdy jack stands to hold it (much more sturdy than the one you have pictured). Plus then you would only need to store one bottle jack and 4 jack stands.
Or whats wrong with the old, drive one tire up on a 2x6 theory? I assume your trailer has a jack in the front to get it on and off the hitch, between driving up on a block and the jack on the nose, I would think it would be cake?