No, it's not insane. It's definitely possible to replace the Xbox DVD drive with a PC DVD drive. First, you need a common Molex power splitter for your PC DVD drive. The Xbox uses a different power socket. Once you have the splitter, simply take out the existing power cable from your Xbox hard disk and replace it with the splitter. Then plug one end of the splitter to the hard disk, and the other end to the PC DVD drive. That's it!

A word of notice though. PC DVD drives are not able to read original Xbox discs. Unless your drive is modified with the specific firmware code, it simply won't read them. The drive will only read from backup dics. Of course this also means that you must already have a modded Xbox for the DVD drive swap to work.