Is it possible to use DYNAMIC_FEATURES while inside a ConfBridge()?
I can not seem to make it work. Have no problem making it work
whilst inside a Dial() but no such luck inside ConfBridge().
Is that intentional? Or am i missing something?
I am trying to get comparable functionality as described via MeetMe()
to be able to add additional people to an existing bridge.

ConfBridge is undergoing a reasonably significant rewrite for the 1.10 release. We opted not to make it line-up feature-wise with MeetMe, but to instead try and capture the most-commonly used or useful features. There’s discussion about this on the asterisk-dev mailing list.