Is it possible to create a hybrid Dvd/Bluray?
No it is not possible to create a hybrid DVD/Blu-Ray disk in the manner which you describe.  The reason for this is that in addition to the digital formats between the two being different the physical media is different too.  You would require a multi-layer or multi-sided disk such as the one you linked to and different digital data on each side.  

DVD players read DVDs using a certain frequency of light and a set spacing between the track grooves (it really is laid out kind of like the grooves on an old phonograph record but microscopic).  BluRay players and disks use a different frequency of light and closer spaced grooves.  Initially this meant it was necessary to have separate laser systems for DVD and BlueRay in any combined player.  More recently optical systems were developed that could work for either format and made combined drives much cheaper to produce on mass.  

I'd suggest the cheapest way would be to get a writable BlueRay and try gluing a writeable DVD to the back of it.  You would need quite thin disks to do this though as they would not fit inside standard drives.  Buying a combined DVD and BluRay disk (and writer?) is the best way to go.