lexan would be ok for smaller electrics where you can get away with 'unibody' type construction. larger models are going to require just as much structure under the lexan skin as they would for any other material, so you might as well use the lightest skin possible. in the low end, you are competing with foamy electrics which are already very light and extremely durable. you are also competing with coroplast, which is completely indestructable and offers fairly decent performance. because of the structure already present in coroplast you don't need much, if any, skeletal structure.

as far as props, breaking props is a VERY good thing! take your choice, crankshaft or prop. besides, the composite props are already stronger then lexan would be in that situation, and there are carbon fiber props if you really want to spend some $$$