To the first point, I understand the developmental argument, the point is it's secondary if he could help us win a championship now, any development can be put on hold if it helps you win a championship. Slightly delaying his development as a starter is not the end of the world. There's also the experience argument that you already made, to pitch in the postseason against the best teams and hitters in the world is incredible. Also it allows our major league coaches to see him first hand.
To the bullpen depth argument, you already made this one as well, there is no such thing, and there never will be such a thing, as too much great pitching. Especially with the way bullpens get used in the postseason. You run through five or six guys a game. You need as much elite talent as you can get and unless you have a bullpen full of closers there's always room for improvement. Every little bit counts. Especially for a team that is going to rely heavily on pitching.
You're right that he may not be ready, command wise, but you've got to take a look at an arm like that at this level. Just try it. Maybe Pete Walker spots something in his delivery and helps him. You never know unless you try. Either it works and we have a stud in our bullpen or it doesn't and you carry out the plan you had. Outside of Kikuchi if he's in the pen, we really don't have a power strikeout guy in our bullpen from the left side. Would definitely come in handy.
Anyhow, it doesn't matter now, it is what it is I just wish the front office was a little more aggressive, especially for a team that's trying to win.