Isn't this over before it starts? Lexmark lost the battle when 3rd parties reversed engineered their cartridge DRM and "reverse engineering for interoperability" was added to the DMCA?
Google by law has to take advantage of these "loop holes". They are a publicly traded and thus by law have the obligation to maximize their shareholder returns. So taking advantage of these tax loop holes they are fulfilling that duty. Doesn't excuse it but it does prevent Google from just saying no we won't do it.
Safety Critical software is really about the confidence level in the software to function as intended and is really language agnostic. This is why most Safety Critical projects focus on development and test practices. You want to have a good warm and fuzzy that the product your outputting will work as intended when needed. The traditional way to accomplish this is through rigorous design processes and robust testing. So no one language has an advantage over another (unless real-time is a requirement which it often is) at the root level. Over the years tools have been developed to help assist in testing and giving you that warm fuzzy feeling at the end. Static analysis tools and code coverage tools are an example. These tools tend to be more mature for traditional languages like C/C++ and ADA thus making them more popular for Safety Critical projects, but that's not to say another language that the development group was more familiar with wouldn't do better. At the end of the day its all about your ability to detect defects and the systems ability to detect anomalies so the tool set that the development team thinks they can accomplish this the best with is the best choice.
Although PhoneGap does not offer any UI elements, there are plenty of mobile optimized UI libraries such as JQuery Mobile and others that replicate a more "native feel". Using a mobile optimized UI library will also dramatically improve the interactive element's and transition's performance. Performance is still a big consideration though as it has more of a good enough versus "native" feel.
Regarding the limitation of "native" hooks, PhoneGap has a very solid plugin system which allows your JavaScript code to call native code. There really is no limitation to this.
As far as fixing bugs, since you are using web technologies to build your app you can usually debug in the the browser. If you have something that relies on a specific device implementation, then there is WEINRE. Granted its not as powerful as debugging in XCode or Visual Studio but it definitely gets the job done without to many headaches.