Something to think about
I did this with some other playout software a few years ago, we used a keyboard (one of those small ones with just the numbers) and took it apart and routed 2 of the keys via the mixer start/stop remotes & it worked a treat.
This way we just assigned actions to keyboard shortcuts
I've made what you want.
Have a read of the following:
If you have any questions, it would be best to post them there.
I nearly went down the MIDI route (and I found a supplier of a potentially suitable MIDI interface) but this looked a good approach and became a "lockdown project".
I do have a suggestion, if it might be considered to add an option that would be able to trigger the players on Play it software from the start/ stop (momentary pulse) button of the audio console ( mixing desk)
Perhaps there would be required a custom made card to be installed on the PC that can interface between Play it software and the start / stop button of the audio console, so the start / stop button of the audio console can start or stop the player on Play it software.
Would not be a problem if it is an paid option to purchase the custom made interface card to install on the PC.