I probably shouldn't comment without seeing him play in person, but here it goes.
My instant reaction to this one video is that his natural game looks incompatible with the modern game. If the limited evidence available here is representative of his broader work, then he's a risky archetype of an already risky position that's recently become less clearly defined (tall forward). His near absence of new school traits means he should, in theory, be easily neutralised by 2v1s. He also looks oddly uncoordinated in one play (like a ruckman), drops a lot of marks (especially in congestion, which will only get harder at AFL level), struggles to ever capitalise on a long kick, mostly marks short kicks to his chest (which small players can do - his height is redunant and not used as an advantage), and in one play he takes forever to make a simple decision to handball to a free teammate standing right in front of him while they're both free... this guy presents as your classic, traditional tall forward who will probably be a disappointment in the modern game.
Still, I do give him points for not being a ruckman.
He is a clunky mover at times, 123. And not brisk. Gets little to no air. Really struggles to catch. Catches some. The footage is a little unflattering.
Correct Jack.
Open Question - How much impact would he have if playing for the losing team? Instead of the all conquering Sandringham.
It's a good question, Bryan. And it harks back to your comment above, 123, about the modern way of playing tall forward.
I think you gentlemen will be aware that until this year Brisbane played Charlie Cameron as their tall forward. He played the role. Oscar Allen plays tall forward. J J Kennedy played tall forward. Post-knees David Schwarz played small forward. And Jeremy Cameron plays mainly as a small forward (high HFF) but often pushes back in for catches and at other times leads up. And then is a tall, who averages 0.5 CM a game.
How does Oscar Allen go in a losing side? He feathers his own nest and kicks a couple. He is a nasty little lurker who kicks goals. Likewise Charlie Cameron, the tall Cameron. They're old-fashioned lurky, leady, sneaky full forwards. (I hate the type FWIW but I have to love in the world in which Armstrong lobs at RFC.)
And when he's a tall inside 50 that's what Armstrong will mainly be. A lurky, sneaky, bludgy, leady, full forward from 1986. Who kicks goals.
Armstrong's inside 50 game is not all about catching, which he's not much good at. He hits the fall and goes again. And again. (That footage above is classic Armstrong.) He runs at goal. He uses towards goal. He will share it. Good values at times and will improve. He lacks aerial game but inside 50 his best play is often post-knees Schwarz like. A bull at the fall. But will share it and can learn more.
Maybe Armstrong's lack of acceleration and altitude will prevent him making the jump to AFL level. But tall forwards are hard to get and an average one is priceless. He has a skill set that is roughly comparable to other tall forwards of the past and present. My thinking is that he is almost certain to be a class above Logan "The Bust" McDonald and McDonald is almost not useless enough to earn a game.
Armstrong has the tank to get up the park and the will. And can improve there too.
He has some weaknesses (OMG those hands) and limitations (can he break into a canter?) but he's there. And he has goal sense. Kicks em. And keeps kicking them.
Caveat: has not been tested at state level. Could he be any worse than Shanahan?