Sounds good about the communication with Ultimaker. They are usually happy to help with such issues.
You might profit from taking a look at the updated firmware E3D made for the Ultimaker, to make it fit their Titan extruder and E3D hotend. I'm using it now, as I have a Titan on my UM2+, Using normal Olsson's block though.
I must say I don't understand the missing parameters in Cura 2.x compared to 15.05.6.
If you add the printer as a Custom printer, there are way more parameters avaailable in Cura 2.4 and 2.5 (Beta) than 15.05.6
Which parameters were you specifically missing in the new version?
I would even go so far as to say that 2.x is a far better match for the paste extrudre than the old 15.x version, as you can independently controll first layer printing and movement speed apart from the general speeds. All sorts of parameters are now split into a multitude of sub-parameters offering way more optimizations options than before.
Aside from my UM2+ I also have an UM2 mechanical clone, but with E3D hotend and using Duet WiFi as controller now, so I have used Cura a lot with different machines. (also had arduino+marlin and later MKS Sbase with smoothieware on the "clone", and used Cura with all of the iterations,)