Stewart has become one of those perfect role players. Everyone one of his strengths compliments the forward line to make it very well balanced.
We've seen Stewart play as what is essentially a hard working half forward/mid-sized player hitting up at the ball, crumbing and laying 5 tackles a match (putting on genuine ground level pressure). He can play deep forward and will either draw a quality defender from Daniher or an opponent will risk a miss-match which Stewart is now starting to take advantage of. His hands above head are getting cleaner and he's looking more confident under the high ball (though odds are certainly stacked against him becoming Hooker-like but, then, Hooker wishes that he could move like Stewart).
The best way to sum Stewart up is that if he was 188cm instead of 198cm he'd still be on an AFL list and playing as a hard running wingman/half forward - that's how good his ground level game is. There are not many 198cm+ guys who you could shorten by 10cm and who would still be good enough to play AFL. That he's 198cm and a pseudo-key forward is all underpants profit.