The plastic barrier your referring to is usually called the vapor barrier or belly board. In most manufactured homes it is the support for the rolled insulation under the floor. If you remove the plastic the insulation is likely to fall out. The vapor barrier also protects the bottom of the floor system and the interior of the home form condensation under the home seeping in. I would not remove it. Why would you want exposed plumbing and electric ?? In any conventionally built home plumbing and electric are run through the walls and floors. In the event of a problem you have to open the wall or floor make the mechanical repairs. If your looking for something that is more cosmetically appealing you might want to leave the plastic in place and overlay it with a ceiling system... Adding heat to and finishing the walls and ceiling of your basement will increase your usable living space and the value of your home.
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