i don’t understand, for my point of view, think there isn’t a development necessary, when it works with bike workouts, then running workouts can use the same interface over the Garmin API.
it’s more a work to configure the Tri-Training Plans ( i prefer Duathlon) so Running workouts sent with the correct pace zones out to the API?
Look on Training Peaks, they send over the API all my bike and run workouts!
i take a look on TR since arround a year, but if this isn’t possible, then i can’t give it a try
would be good for your business, to get more customers, for example:
i pay for Training Peaks Premium, i pay for a Trainings Plan there, i pay Zwift (Training Peaks import works automatically)
when Trainer Road make this things possible, i only have to pay to Trainer Road (thats good for you)!
seems Trainer Road have to change their profiles for hunting developers and so on @ https://trainerroad.recruiterbox.com/
sorry, i am only kidding, but never seen so fucking cool job descriptions ever! 
