When we look at Mr. Kimishima's history, we can see where his priorities lie:
1) Worked for 27 years at a bank in management positions
2) Worked as Pokemon Co.'s CFO
It's clear that finance and business administration are his strong suits. Presumably, Kimishima was great at running the day-to-day operations of Nintendo of America.
By taking more of a back-seat / COO role in the company, it avoided any potential clash with Iwata, and it allowed the subsidiary to maximize efficiency in logistics / localization / sales. In terms of running things Iwata-style, Kimishima being a passive CEO out of the spotlight allowed Iwata absolute control.
See this photo?
From left to right:
1) Joel Hochberg, president of Rare Ltd.
2) Chris Stamper, co-founder of Rare Ltd. and project lead on many classic Rare games
3) Frank Ballouz, NOA executive
4) Howard Lincoln, senior vice president (eventually chairman) of Nintendo of America
5) Minoru Arakawa, founder and president of Nintendo of America
This is a photo taken at the legal signing of a contract made between Nintendo of America and Rare Ltd. in 1986 where Rare Ltd. would produce games for Nintendo arcade systems.
Where's Hiroshi Yamauchi? He was back in Kyoto, uninvolved in this deal. That's right---Nintendo of America signed a game development contract with Rare Ltd. without the oversight of the Kyoto office.
Can you imagine the modern Nintendo of America going to Warner Bros. to commission an exclusive Batman game for the Wii U? Or what about even for a simple GTA V port?
It's unthinkable to imagine today's Nintendo of America making game-development-related business deals without Iwata / NCL involved---Iwata becoming NOA's President / Chairman solidifies that. Iwata has buried himself within every facet of Nintendo that getting rid of him would be harder than you might expect.