Hi,
indeed these proxies where not design to be added at runtime.
I checked and there is a way for me to create actions for each system events, so let me work on them and I'll push a new versions, and you'll be able to catch any Unity UI events without any proxy which will be better for templates that runs on any object.
however the solution is also to simply compose your proxy by adding it to all objects potentially running your template and your template catches the default event setup on that proxy, this should work too ( but nonetheless, I like what I found on the doc on 5.6 so I'll implement it anyway)
Bye,
Jean