I would setup a "coffee fund" for donations for the software - i have found people to be generous if you leave a paypal/venmo/patreon link for $5/25/50, and set your own price points. Or whatever amount makes sense to you.
The other options is the board - if you have to time and desire you could build a few combo kits where it's the board, screen and software then another kit that includes that and the stepper motors or whatever sort of makes sense. Some people want turn key - they want to be able to build it but it needs to be accessible to them. The more you "do for them" the more premium kit it is hopefully with a bit more margin for you. This may or may not be a good idea depending on your desire to keep inventory of items and "kit it".
Those are my ideas.
Now for marketing - what is it about the Clough42 interface that you don't like or from the other side; what makes your interface better? I've been following along and am very impressed with your progress. I will say without some time investment i don't know the approximate cost of the ELS however i'm not sure i know that with the Clough42 setup either.
For the Clough42 interface, I don't care for the small button presses and 7 segment display of information. This is more or less an interface from the 1980's. I want to see the choices of threads and feeds, in clear fonts, rather than scrolling through a list one by one. Pushing a small button repeatedy to expose the 24th item in a table is not my idea of a good time. I have tables of threads and feeds, whose value is selected by your fingertip. What I have, at least to me, is more user friendly. I have a safety interlock of sorts, the stepper is disabled, unless it is deliberately enabled by the operator, by pressing a clear start button. Hadn't really thought of a sales pitch on features, but maybe I should. The controller is small, very compact, and readily available. The Teensy is 1" x 2.4" and rather robust, the TI board is 2.3" x 6.15", nearly 5.9x bigger, and you here of people frying them or having difficulty programming them. The Teensy runs at 600MHz, the TI system at 100MHz. The TI system does have it's advantages for development, but it is a significantly less modern processor. The Teensy can take advantage of most of the Arduino software libraries. PJRC, the developer of the Teensy has certainly invested quite a bit in writing and maintaining some pretty advanced libraries.
The cost of an ELS system is dominated by the motor, driver and power supply. This of course does not value all the time and effort into making motor mounts and designing mounting schemes for the encoder. I know I spent a lot of time on that. The controller, PCB, display and box are a bit less. Retail HW costs would be on the order of $75. The motor system is on the order of $110+, going up rapidly depending on what you are trying to drive. Then there are the various pulleys, belts or gears that you need and are custom to your lathe. I haven't added that up yet, because I bought extra stuff, trying to figure out what would work on my lathe. Oh, and you need to be able to broach the pulleys and gears, or they may not work on your lathe.
As for a business plan, I'd have to listen to what people might want. They'd have to be patient in the beginning, because I can't afford to be stuck with expensive inventory. So I'd have to build per order, at least in the beginning. If things picked up, then I'd have more options. Clough42 makes money on the hardware. He gives away the software. Personally, I don't know how to make much money on the software, but quite honestly, it is where most of the intellectual property actually resides. In my case, I knocked off the board design in a couple of days - starting from never having used the tools or ever having made my own boards. There's some IP in the board design, but it is easily copied.
