Garmin Coach - Run Walk Datafield

For anyone using the Garmin Coach adaptive training plans, it seems one limitation is that the built in run/walk timers available on the watches do not function when doing a 'coach' workout. For the Coach Jeff plans this is quite an oversight as some of the runs call for over an hour of run/walk.

I had the idea of using a datafield to replace this functionality - it would need to allow the user to configure the length of the run portion and the walk portion, start these timers on a new lap (the coach workouts record a lap each time the segment changes i.e. 5 min warm up, 30 min run/walk, 5 min cool down creates 3 laps), and then alternate between run and walk until stopped with vibrate and/or audio alerts when changing from run to walk and vice versa.

It sounds simple enough but maybe its not!?