The plastic cladding was an afterthought to an existing chassis so the car was heavy.
The s-series was NOT a unibody-- neither was the fiero. Both were space-frames.
L-series was a traditional "something else" reskinned for marketing reasons.
That all said, the wagon has a nice cargo compartment-- almost volvo-sized, and good visibility. There aren't many midsize wagons out there, particularly with the transverse 4 cyl, for you misers out there. The volvo, its only competition that I can imagine right now, might be nicer but has its own share of expensive problems.