No to Jai Courtney. From the little I know of Pym he strikes me as a workaholic scientist first, superhero second, Courtney just seems all wrong for that.
From jaquas Ultron post in the other thread I'm going to pose my fancast for Pym - Ewan McGregor.
In flight there is serenity - the motion out, the space between,
The promise of each new life - and possibility.
Swallow flies south before the fall, before the winter can call...
Can call in each borrower - for what was given
--Serenity in Motion--