Sorry missed this, but yes - totally doable, but will cost a bit!!
One way with Harvestman / Industrial Music Electronics Stillson Hammer and Argos Bleak.
Set the chords up on Argos Bleak
Set 4 steps, one each to the correct voltage to trigger the chord in Argos Bleak, then set to play on random on Stillson hammer MK][ for 25% probability. To increase the probability distribute the voltages across the number of steps in your sequence - think about what having two steps on the same voltage in a 5 step sequence on random would do to the probability.
Another way would be with Monome Teletype - it would involve creating a look up table for your chords and some programming to determine the probabilities, but probably a few ways to achieve this.
The Teletype will have more fine grain control and precision, the Harvestman will be more 'tweaky' and more fun to play :)
Hope this helps... :)