First of all, Vickery is perfectly capable of playing as a forward, at his best he's a 40+ goal a season player. He played as a forward in the u/18 carnival and at TAC level and he's not looked out of place as an accomplished AFL forward, in fact I recall Emma Quayle's assessment of Vickery as being even money to be a key forward. In light of all that, I can't see how you could pigeon hole him as a ruckman, particularly when he's just undergone a shoulder reconstruction.
If Vickery, Elton, Griffiths and Astbury are all competeing for the same spot, then that's a healthy sign of the state of our list I would have thought. I wouldn't be rushing Grundy into the frame prematurely in any case, he'd been see as insurance in his first season and even beyond that. Ultimately he should be seen as Maric's heir apparent, not some surplus requirement who's sole purpose is to force other players out of the side.