Um. You do realize that all you need to plug a FW400 cable into a FW800 port is a cheapo $5 cable, right? And you also realize that Apple will never, ever make a Mini DisplayPort to S-Video or composite video adapter? If you absolutely need to hook up your 20-year tube TV, just get the DisplayPort to VGA adapter, and get a VGA to S-Video/Composite dual-purpose cable. They're $10.
If these unrealistic issues are the actual reasons that are holding back your purchase, I have a newsflash for you: Apple will NEVER manufacture a laptop for you. Hope you enjoy never owning one!
Seriously, either buy one or don't, but don't manufacture "issues" that either have solutions or will quite obviously never be addressed.