Confused about RMS & catastrophic engine failure

[cplus]

Let me preface this by saying that my '02 Box has not had an RMS or catastrophic engine failure that I know of. This question is just for my information. That said, posts on this forum have me pretty freaked out about RMS failure to the point that I look over the floor of my garage whenever I pull the car out to check for oil.

I understand what the RMS is, what it does and how it can fail. Further, I understand that if a Box suffers an RMS failure while the car is parked, it will be flat-bedded to a competent mechanic to have the transmission dropped and the RMS replaced. The owner will likely be facing a four-figure repair bill, but otherwise no lasting harm done (aside to his/her checkbook and marital harmony about spending the anniversary vacation money on fixing the car).

What I don't get is what happens if a RMS fails at speed, or more specifically why an engine may need to be replaced if the RMS fails. Based on my own experience with an oil filter seal failing on a lumbering American V8, when the seal fails at speed, all oil is evacuated from the engine; without lubrication, pistons start scraping against cylinder walls, cams may become scored and bearings eventually sieze. The motor seizes, but chances are good that it can be disassembled and rebuilt.

So if someone were to have a RMS failure at speed, and they noticed the plume of smoke from the back of their car and shut the motor down immediately, why couldn't it be rebuilt? The motor would need to be removed, and probably honed, maybe new pistons and/or bearings installed, but it should be salvageable, no? Even if they didn't notice the smoke and drove the car until the motor siezed, could it not still be rebuilt? It's not as though they put a rod through the block.

In a nutshell, my confusion is that I'm under the impression that Porsche flat-6s can't be rebuilt. With the cost of used 3.2l Porsche motors in the high four-figure range, and 3.4l Carrera motors in the $12-$15k range, I'm wrestling with why a Boxster motor couldn't be rebuilt more cost effectively. Sorry for being so verbose.