My thoughts on Jordan Larmour are that if you have a potential world class talent and a short window in which to prepare him for the 2019 World Cup, you have to blood him. Nine months ago, Andrew Porter, James Ryan and (less so) Jacob Stockdale weren't ready for international rugby. They were given a chance last summer and look at them now.
Larmour is worth persevering with and learning on the job. I suspect he'll see a lot of game time on the Australia tour this summer where he'll be out of the spotlight more so than during the 6 Nations. There's no point in waiting longer.