The Lions bolter

The expected dirt-tracker who will probably (maybe) not set a foot on the pitch in the first test.

But his form and the local conditions make him exceptional.

Extraordinarily I suggest either of two Tigers:

Tom Youngs : An ex-centre to emphasise his speed and mobility (if he can chuck straight).
Tom Croft : Currently the cleanest, smoothest and most effective line-out taker in B&I. Not a slouch around the park. Good for a try or three.

Surely the bolter is someone who actually does make it to the first test, the guys who don't aren't bolters?!

Besides of the squad I expect Youngs, Stevens and Lydiate as about as far from a test spot as humanly possible!

If you are talking about bolters, you can't really use the names of establish internationalists.
To me the only potential bolster in the party is Sean Maitland but I don't see him getting in the test team

I thought if there was going to be any bolters it would of been someone like Wade, Madigan. Players that have not been selected but maybe called up in case of injury.

There couldn't be any more of a bolter than Tom Youngs - new to the position as well as Test rugby. Gatland has staked his reputation on taking him ahead of Best who would undoubtedly have been in Test contention, so Youngs can't be a dirt tracker.

How can Croft be a bolter? If nothing else, he's already a Test Lion.