Hey man,
Josu Vess, Lich Knight would be a superb choice in my opinion. The kicker cost is quite high but certainly not absurd in EDH, but the power you get from it and the sheer number of bodies seems like a great match for Aryel who wants Knights to tap.
Sigiled sword of Valeron does a pretty good job of getting knights on the board too.
Not sure if you're familiar with it, but EDHRec is a great resource for
inspiration when building around a specific commander. Well worth a look if you haven't already.
Good luck on your quest!