While nice, there are several problems with this:

1. You can't use HTML compression methods with vShare as it compresses everything (including your media). The media won't work if it is compressed. You can use mod deflate (since it can be configured to certain file types), but the compression rate is not as good and it will still trigger this with sites such as SEO Site Checkup. Likewise, the current version of vShare (2.6) is in binary format and cannot be compressed any further. So, the only real compression that you could do is optimization on your templates.

2. There are two different types of caching: browser-side caching and server-side caching. vShare uses server-side caching which aids in keeping server load down (everytime you access a PHP file, the server has to compile it before sending it to you. By caching on the server, you can cut down on resource utilization since PHP does not have to recompile the cached versions everytime they are accessed.). The way vShare caches (in 2.6) is actually kind of pointless because the source is encoded with Zend. Since the files are already binary (which can't be compressed), there is no point to caching them, which is why vShare caches the templates. However, this does you no good because by caching the templates into a PHP file, they must be compiled which adds a bit of load. This is one of the things that I plan to tweak with the next version coming out tomorrow. Browser-side caching, on the other hand, would not be beneficial for a tube site because the content is constantly changing. The point of browser-side caching (which is what X-cache is by the way) is to not have to load static pages. Since vShare is dynamic, this would not work.

3. Image expiration tags would not be good either for vShare. Since the pages change dynamically (for example, if you have recent videos on your main page or recently viewed videos, the page changes with each visit), using code like this would cause people to massively download and store images to their computers on each visit. The performance of your site, as a result of this, would suffer as the current version of vShare does not compress the images that are generated (something else that I am planning to tweak with tomorrows version).

All in all, the SEO issues that you listed here are common for any tube site. For example, run the check on YouTube.com and you'll get the same results. Unfortunately, our type of sites are going to run into those issues.