Even if you have your own ISBN numbers and you want to have the book available for libraries then you'd need to use a CreateSpace ISBN as that is a stipulation for that channel of expanded distribution. How likely are libraries to be to purchase a copy? Standard distribution and expanded distribution (with the exception of libraries and academics) are all fine with your own ISBN; it would only be limited by that one distribution channel.
The only way around that limitation is to not use CreateSpace for expanded distribution and to go with another service, such as Lightning Source or Ingram Spark.
If you are not going to promote your book heavily to libraries, you can make your book available through CreateSpace with expanded distribution and if it happens, then that's a bonus. If your strategy will include a lot of promotions to libraries (or book stores) then you should dual publish to both CreateSpace (and to turn off expanded distribution) and also to Ingram Spark (or to Lightening Source if you have a large enough catalog.)
Your Amazon sales will be sold through CreateSpace, and all other sales will be made through IS or LS. This will give you a higher profit margin and more professional appearance.