In the Reaper Arranger video it had glitches from screen recording software and trying to capture the video and audio at the same time with the onboard audio device as well as too many other things running at the time, if you try Reaper with the BBPlugin and smooth seek enabled in the prefs/audio/seeking while you play Reaper back with the BBPlugin following then click on another bar and it will go there smoothly.
The Arranger script I made simply works by reading the midi chord input and going to a random chord region of the selected color and loop it until another chord is entered it will then to that chord/color region.
You can set smooth seek to change on next marker or next bar/s.
You should try out the smooth seek using the BBPlugin and you will see how well it works you won't get any glitches.
Just generate up all the chords you need 4 or more bars long for each chord.
If you use 2 BBPlugins you can have all the blue and blue ending in BBPlugin 1 and all the green and green ending in BBPlugin 2 and Plugin 2 is set to sync start on the bar after BBPlugin 1 ends.
You can drag the C7 out into Reaper to get the chord markers, drag the BBPlugin 1 C7 to first bar and BBPlugin 2 C7 to where it starts.

That new RT RD Ketron Event keyboard uses an OS as it has an SSD in it, could be a damn small linux ?