The thing everyone needs to keep in mind is that while you may like the look of prosilver, and we were able to hack in some responsive features. Their are way more reasons to create a new theme then just the visual ugliness of prosilver.
The fact of the matter is the code base has become antiquated. The entirety of the html needs rewrote and the css needs completely rewritten to be cleaner and more organized not to mention modernized, weather you still want to keep the visual appeal of prosilver or not, to allow for phpbb to progress into the modern era of the web. We also need to build it as a mobile first theme to truly take advantage of responsive design.
Instead of being able to spend time on progressive improvements we have to hack the theme into submission which is not always easy.
I get that people do not like change but the fact is that change is a necessary thing and adaptation is the key to progression. We can totally create a theme that still has the prosilver feel to it without having to use any of the original code.
I do like the idea of angular.js and ajax everything...
As far as bootstrap goes. I am half and half on that one its come along way recently, but it still lacks in my experience true organization. I do not feel that bootstrap should be used as is but customized into a framework that we can get behind for the future of phpbb.
Let me clarify.
instead of including the entire bootstrap file we should instead only use what we need as individual objects. As well as further divide/separate those into a better system of organization. a theme consists of several pieces if you look at Atomic design. objects which are like your models in an MVC, components which would be your controllers, and pages which would be your views.
example of what i mean all the buttons in prosilver should be an object called button. all posts would be a component made up of several objects like the button class. Then at times we need to alter the appearance or placement of these components based on the page or. IE how is a post display differently from a viewtopic compared to a post preview page their might be a slight style change.
Then their are subtle changes like a simple color change to a button(IE different color or size of button) in one section as apposed to a different kind of button in another these would rely on override classes referred to as atoms, think of these as modifiers
This allows for far better code management as well as extensibility as everything is its own object and can be separated out into its own css file to be combined/minified/gzipped and cached someway via the core.
Its still quite early on, but I have been working on something along these lines for a month or so now
https://github.com/hanakin/mino if you want to check it out or provide some feedback.
One of the other big things we need to allow for is the breaking of the mold. We need to allow for the in how things function and what is needed from a UI outlook. IE is it acceptable in some cases to add an extra click if it saves screen real-estate, is the feature really utilized, or is their a better paradigm for how the system should function.
whit your borders we will need 1 hour 
