We have looked at it. Repeatedly. First when porting Chrome to Linux (and trying to decide what sort of UI there should be for NSS cert management). Then for ChromeOS. And then again, revisiting it in light of the OpenSSL migration.
The reality is, the certificate management/configuration UIs, of all platforms (Windows, OS X, Linux-via-Firefox-and-Chrome-which-just-copies-Firefoxes-PSM), is hard. It's hard to express the decisions. It's hard to explain how the branching and cross-certifications of CAs can affect trust decisions (eg: recall DigiNotar's cross-certifications).
And in the end, it's not where users are spending their time/being tripped up. Getting the lock icon into a more meaningful state is a far, far greater investment, with far, far more actionable returns in users security. The work of the Chrome Security Enamel team on this - especially Adrienne Porter Felt - has been focused on trying to improve this.