If you're going to settle for 20% of your starts to be from kids who "may or may not surprise", why not trade everyone and start a new rebuild? Because what you suggest sounds to me like trying to contend for a wild card slot, at best. Maybe.
The Cubs have a rare window, here. While you still have Bryant, Rizzo, Contreras, etc., I think you have to go all in. And, at least in my experience, you're not going all in to try and win this year by going into spring training witb four decent starters, one swing guy you'd rather keep in the pen, and some kids who have little to no experience pitching in the majors. They thought they could do that last year, and were the third best team in the division until they bit the bullet and traded for Quintana. After which they maintained a better winning percentage than in '16.
It would be a crime not to support this core with the pitching it needs to not just tread water, but to aggressively go for another championship. IMHO.
Edit -- meant to quote Diehard's post about biding time, not signing any more pitchers, and seeing how well that works out. Sorry, made less sense out of context.