Idiom-related quibble: a "double edged sword" typically refers to something that is both an asset and a liability.
Higher production costs and more built-in defects are two liabilities. A suitable alternative in this case would be a "double whammy". More on that idiom: http://english.stackexchange.com/a/132063
You do realize that this is a good argument for the Tesla, right? An electric drivetrain is much simpler than a gasoline one, and in a crazy features battle, the S Class trounces a Tesla.
I heard this from Musk before, on first sight it makes sense.
BUT - most current failures in cars are not components that are around for 100 years - these are usually fine if regular service is done. What fails miserably in new cars are all kinds of tech gimmicks that improve significantly with every new generation.
The only exception might be turbo charged petrol engines, but they are around for a while too.
In my personal experience, what breaks on cars is run of the mill stuff that's been around for a long time, like tie rods, brake roters, the exhaust system, et cetera.
One of the more expensive and annoying repairs I had to have done was the end of my parking brake cable snapping off when I pushed on the pedal. A few cents of metal turned into many hundreds of dollars because the whole cable had to be replaced and it was routed stupidly requiring a lot of labor to disassemble and reassemble stuff. I dare say that cables and their attachments have been along much longer than 100 years.
Other mundane repairs include tie rods, exhaust system leaks, and premature brake rotor wear.
On the other hand, in a decade of car ownership (not a huge amount of time, to be sure) I never once had to repair anything relating to the newer features of the car like remote entry, computerized engine control, digital entertainment system, etc. Even on my 2005 GM, which was not the best year for that manufacturer, it was the boring, old, "proven" systems that needed attention.
I now own a Model S and my maintenance/repair worries are almost all about the boring mechanical bits. I already had a sunroof problem where it got jammed (fixed well and without hesitation under warranty, of course) and when I feel like worrying about stuff on the car breaking, I worry about the little motors for power seats or door handles failing, or the hardware that holds the wheels on starting to bend. The fancy systems like the autopilot stuff seem to have nothing that's likely to fail.
Cutting edge tech = higher risk. (can be mitigated with engineering discipline)
Small production runs = less time to debug production process, which is a 2 edged sword: higher production costs and more built-in defects.