Simon is a perfectly good Bible name. Jesus wasn't declaring the name to be bad when he renamed Peter. Besides, there are other Simons in the Bible, including another apostle. The name is not obsolete (and is quite common in some parts of the English-speaking world).
That said, I don't think I would name a kid Simon Peter. Not because it isn't spiritually allowable, but because it might burden the kid with a name that to some people could sound over-the-top or presumptuous. Imagine the teasing: "Your name is Simon Peter? Really? Hey, can you get me into heaven? Want to go fishing after school?" You put your kid in the position of having to respond either to biblical joking or to Catholics and others who find his name to be uppity, which probably is not something you wish for the kid.