You could just leave the older versions compatible with the older versions of NodeBB. Like currentlyat BitBangers, we have the old 0.0.6 version running as that was the only one i could get working correctly with the 0.3.2 version of NodeBB.
If you use an older version of nodebb then you will have to use an old version of the plugin.
Having to scroll through the forum threads to find a nice looking theme or an interesting plugin is cumbersome (at best).
It'd be nice if there was a dedicated website where you could upload your plugin/theme, and i would read some JSON and display all the themes & plugins based on the info in that json, properly categorizing everything and showing easily viewable thumbnails of the theme/plugin in action.
Ideally there would be categories and tags that you could filter by, and all of it searchable.
Just a thought/suggestion (and sorry if someone already suggested this!)