Yeah what leo said, it might well fit things into it without issue, but due to the way they mass produce things, it can be very hard to guarantee compatibility with standard components.
Additionally, you miss out on modern features that while not essential, are going to be beneficial to almost every build.
As for the optical drive, the major difference between an older one and a newer one is that these days they are all SATA rather than IDE, and most motherboards these days don't have an IDE connector. You might need to replace the drive, but at least it's cheap.