good ideas here.
As I write this post, I keep changing my mind about whether I like Seeker. Outside of ruins games (or maybe terminal collision), it seems rare that anyone besides the Seeker-player would flash an action card to Seeker. It seems okay.
The idea with Iron Smelter is to flash your cheapest cards, so when everyone else flashes a copper, you have to have a pretty bad hand in order to activate the better effect (unless you have a madman, spoils, and/or prizes), but +$3, +1 buy a still a pretty good $5 cost card, and the unpredictability of it is probably balance enough.
Preside is nice (although weird as an attack because more often it'll be a benefit to the other players). Usually a strong gainer with the drawback of letting other players trash a copper.
I really like Cardinal (despite not needing the 'flash' mechanic), though it might need a minor nerf. +4 cards, discard one (as it will usually be) is still stronger than most smithy+ cards even if it didn't have an attack on it. EDIT: Then again, the attack is pretty weak, so it might be fine.
Blueprint and Gleemen are the only ones here I don't like. Blueprint is a dud, and Gleemen doesn't look like it'd work well. After a couple plays (if not at first), everyone will flash a treasure.