Absolutely, the more blues the better.

http://berkshirequilts.com/freebies/JacobsLadder.pdf

here's a scrappy Jacob's Ladder - should help you picture a scrappy inner border. I'm not sure if I would size the navy inner border segments' length to be equal to the size of the blocks or not.

Here's a border similar to what you are describing. Using the florals from the main quilt, I cut the strips into different lengths (3" - 6" I think) and joined them all. The only part of the planning was to not join two of the same strips together. Gosh ... reminded me ... I still have several feet of these strips sewn together I can use on something. I was originally going to bind the quilt in it but decided against it.

i love making scrappy borders!

yes indeed, you can make it work! Bet it'll be beautiful!

You certainly can and I think that, as someone else said, if you lay them out and 'eyeball' them, you can tell if they'll look good or not. (Let me tell you a secret. There are no quilt police! LOL)