The single lever controller would require a little rework but should be do-able.
The single lever is just a spring-loaded rotary switch, where there is no contact between any pins when it's at the center (resting) position.
Unlike the newer controllers with the three paddle-style buttons, the single lever does not energize the meter circuit unless you move the lever partway right or left. This also energizes (releases) the brake. Pushing the lever all the way right or left keeps that energized, and also engages the motor CW or CCW. You could easily put the CW and CCW dry contact relays across those two portions of the switch. However, nothing would happen unless you also energize the rest of the controller.
There are two transformers in that unit - Power and Instrument. Both have 110 volt primaries. The Power transformer has a 26 volt secondary and powers the motor and brake. TheInstrument transformer is 23 volts and is physically smaller (lower current capacity) and powers the metering circuit and lights. The primaries are wired in parallel - moving the lever right OR left connects one side of each primary to one blade of the (nonpolarized) power cord. The other blade of the power cord is permanently connected to the other side both primaries through a fuse.
So, if you want to retrofit such a controller, I'd suggest bypassing/replacing the lever switch altogether. Add a toggle switch to energize the primaries of both transformers, a relay to disengage the brake (secondary of power transformer to rotor terminal 2), a relay for clockwise (power transformer secondary to rotor terminal 6) and a relay for counterclockwise (power transformer secondary to rotor terminal 5). Those three relays would be driven by the interface of your choice, such as the K3NG Arduino interface. This would also provide a continuous meter indication (rather than only when you move the lever).
There are known issues with ripple on the directional pot on the rotor because the center of the pot is common with the motor common terminal. I've seen some blog postings about various ways to deal with that but haven't really looked into it. Shouldn't be too difficult with some filtering.
If I can get around to it, I may do just that with one of my old Ham-M controllers so I can use it for the azimuth rotor of the satellite station I'm slowly automating.
Note - there were more than one series of that controller, and they are NOT all identical. The above refers to the Series 5 controller, which I believe was the last one of the single lever ones. The numbering in the schematic I have does not make much sense when looking at the actual switch, but it's pretty easy to trace and figure out what is what. I have a picture of the inside of one of mine, and I documented which wire goes where, but your mileage may vary.
Good luck whichever way you choose to go !
73 de W0ZF