Ok and Exit buttons can't be remapped (easily).
For all the other remappings download the plugin MultiQuickButton.
It's not very easy to understand and configure, so initially some try and error will obviously occur...
Be advised that using that plugin a very few default button functions will be no longer active, for example the Green Panel, or at least I was not able to make it work (however this is not a big problem to overcome).
In the whole, I think that using MultiQuickButton is a big step forward in using the Vu+ remote!