In my point of view there is no outer page rank. There are only two types that is home page rank and inner page rank. Internal pages with good pagerank can have significant impact on Google rankings of that specific page.

I don't really think the distinction is of any value. It's just 'Page Rank' in my opinion. Rank of the page. Doesn't matter if the page a home page or not.

But that's just my view.

Just wanna refresh this thread...

Bookmarkings and deep linking would greatly increased internal pages' PR

Have good content and then get good links coming in to that specific page from authority sites.

Maybe you would like to rethink about the focus.. making the inner pages PR4 has no value to the company and it may waste more money.. However, if your company is going towards that direction, make sure the site has a text link internal linking structure (this is the most important factor).