No, oil-based will not work as well. It will take far longer to dry and because you will be working with a hydrophobic work surface, the spread of the oil-based will be uneven and dry uneven, whenever it does decide to dry.
Water-based is a bit of a misnomer. Just because it is water based does not in any way mean that water will dissolve it once it is applied. It is just a plastic that is suspended in an aqueous solution. Once you seal out all the pinholes through multiple applications of the poly, you should be well sealed from any moisture. Further still, once you apply paint over top of that, you have an additional seal of moisture.
Example: 72" span scratch built Sikorsky S-39 covered in mostly fiberglass but also tissue paper and water-based poly. I've had it out in very moist conditions as well as in a pool for some float testing. I've only had issues with the covering on HOT days, when the foam off gasses under the glass and creates bubbles in the glass.
Water-based is a bit of a misnomer. Just because it is water based does not in any way mean that water will dissolve it once it is applied. It is just a plastic that is suspended in an aqueous solution. Once you seal out all the pinholes through multiple applications of the poly, you should be well sealed from any moisture. Further still, once you apply paint over top of that, you have an additional seal of moisture.
Example: 72" span scratch built Sikorsky S-39 covered in mostly fiberglass but also tissue paper and water-based poly. I've had it out in very moist conditions as well as in a pool for some float testing. I've only had issues with the covering on HOT days, when the foam off gasses under the glass and creates bubbles in the glass.