Hey Brian,
It sounds like you are onto a good niche idea. Remember this - even though you may think you'll never be able to beat the 'big 3' in your category for the MAIN keyword, there are going to be a ton of other keywords that you'll write pages about that you can rank #1 for.
Here's something to think about - my chocolate site? I was "found" for over 5,000
different keywords and phrases last month. I may not be in the #1 position for the phrase 'chocolate candy' but I am for enough other phrases (or close enough) that I get more and more visitors all the time.
You're going to find a ton of phrases that people actually use that you hadn't thought of yourself when searching for information in your niche. You'll get found for those as you build more and more content.
It's good that you have a general layout/design in your head of what you want to do, but as you go through and do some brainstorming, allow the information/results to guide you. You'll make some possible changes and adjustments as you go along.
I'm dying to know what you niche is!

When you finally get yourself up and running, do be sure and let us have a peek at your site.
You're right about beating 95% or more of the sites in your niche. The majority of SBI sites rank in the top 3% of the traffic rankings. Why shouldn't YOU?

Blessings,
Angie