The minigames are great fun, but unlike everything else in the worlds of the Spiral, they stay the same wherever you go.
While it would be a bit of work for KingsIsle to make entirely new games, I was thinking they could have different graphics for the games in different worlds. Imagine Dueling Diego who goes to MooShu: replace his sprite with Samoorai Sam, change the background to a dojo and such, perhaps change the obstacles/enemies as well. The gameplay would be the same, but it would add a fun "spice" to each world.