I use vMix for AV support for conferences as well as on my video wall TV set. I would love to have the ability to transition the video displayed on my Fullscreen output instead of the basic "cut" being offered now.

I can think of two ways to offer this feature without cluttering up the UI:
1) Right click an input source to Quickplay to Fullscreen Display 1 or 2
2) Use a shortcut call to set the source for the Fullscreen Display output and with a transition or overlay option

Either option works for my needs. The only other option I can think of right now is a dedicated Fullscreen Playlist input source with transition option when advancing or changing Display sources.