Apparently child will tell mom when they need to go (very verbal in other areas) and will start "holding." I really prefer kids be able to do some portion of the routine independently, but if it's as cpnsistant as they say, I'll give it a shot. Really the only reason I like them to be independent is so that I don't have to leave the little ones alone as long... And really, he's the littlest one.
I don't have huge expectations and I already made it clear that he needs to be in a diaper this week and if he's very successful and moving on, he'll be put right back in trainers or diapers if he starts having accidents again. If it works, that's great, but I'm all about training the child, not me. For me to take him every hour at 16 months is not going to help anyone, just add to my workload, so if he's not communicating it to me, we'll hold off.
Sounds like you have a great plan to satisfy the parents request to train but also to have boundaries on what you are prepared to do for training at this age. Good Luck and let us know how you get on