Hi Abdelwahed,
I don't have any experience in Propel or Doctrine, but if you have experience we can talk and see if we can make this integration, sounds interesting to me.
If you are searching for any ORM you can use RedBean, which is already part of RainFramework, and is really easy to use, or you can also keep in consideration to install a NewSQL server, like Akiban, which allows to get the result in JSON or native PHP Objects, also has great performance thanks to the groups, which are like the views, but way faster because the row in relation are stored in the same area of the memory.
Let me know,
Federico.