I'm really thinking it needs to be functional and not bogged down by the traditional sequencing and visualizer limitations. A lot working at a high level and less done at individual display item level. But you can mix and match as desired.
I'm thinking you start with a bunch of hardware with various capabilities. You set those up once, and just maintain that collection in one place only. This software must be able to handle various technologies, protocols and interfaces ... both commerical, DIY and standards based. It must be easy to reconfigure the display from year to year and able to transition lots of items easily ... per item, per group, per controller, or from visualizer input.
Then you start creating groups of 'display items'. There is no limit to how big or small these display groups can be. You can also put any item in your display into any number of display objects. There is a big cross reference being created here. The display groups can have smart characteristics that are definable and configurable. The goal is you start building out a set of higher level display groups, to save on sequencing.
Some smart effects that are created would be specialize to deal with common things like arches, megatrees, rgb strings, rgb matrix, left-to-right, right-to-left, top to bottom, fans, spinners ... fading (directional fading). In addition, these effects can be defined, shared, imported (think google earth objects) ... and layered.
Then at one level, sequencing would be defining broad actions, effects, and transitions between these display groups ... possibly implemented in a similar timeline form to current sequencing software.
At a higher level, there could sequencing macros created which infer that once you do this, you also do this, then this ... and those can be stretched across time like a chase and time warped on the fly as needed.
And along with this is a very realistic visualizer which might even offer point and click sequencing options for those wanting to sequencing or paint a picture (as mentioend earlier) in a paint by numbers kind of way. You could draw boxes over top of the display visualizer and those boxes could be used to sequence with and do high level sequencing, but you could always go back to the traditional sequencing view to fix some things afterwards.
I could also see a point with a voice guided sequencer might work to some extent. You would direct the sequencer with commands: "begin a left to right fade, all items, red only, 30 to 100 percent, go" ... ok, were getting crazy here, but its fun to think of.