I had ran across this some time ago, but forgot all about it… thanks to Klaus for giving me a link to get some research started back on this.
The Kitchen Rudder is a mechanical "clam shell" arrangement that can be used with a fixed prop to provide steering and reversing through moving the clams in various configurations. The reversing functionality reminds me of a jet aircraft’s thrust reverser, if you are familiar with those.
The design was used by the British Navy on smaller launches, etc. for some time, apparently.
I had the thought of combining this with some of the electric motor "pods" for steering… would be a different alternative to the "steerable pod" that is seen, although I think that would probably be adding complexity instead of taking away. You don’t need the "reversing" aspect with electric, but the steering you do, and the advantages/disadvantages to a prop shroud are still there. Similar to a kort nozzle when in "forward thrust" mode.
The original patent seems to be 1,186,210 (click the "Images" button at the top)
A later related one is 4,895,093.
I’m attaching a writeup and graphic I found at the Artemis Steam Launch website.