Can you cure pork belly with skin and not replace the water?
I'm not exactly sure what you mean by "not replace the water".  Pancetta is cured using a dry cure process.  This does result in water/liquid leaching from the belly.  It does, of course, become part of the cure, but it is a dry cure, as opposed to a brine cure.  In any case, skin on or skin off should not matter. I prefer the flat pancetta (and leave the skin on) to the rolled when home curing. Add your salt/spice mixture.  I usually use the "salt box method".  I place mine in a ziplock bag.  I like to place a pan with a pound or two of weight on top, this keeps it flat.  Flip the bag every day until the belly is firm.  Rinse, pat dry, and proceed with drying. I find it one of the easiest, most reliable, home cures to do.