Yes Alcan is off the charts for silliness that you can practically apply to jacks. So make it Defender's ward so that he can put it on troops (so he doesn't completely ignore troops), or remove it completely. My point is that any caster is a "jack" caster because they can't control warbeasts. What you can do with those jacks to augment them beyond focus manipulation and abilities comes to spells. Abilities are nice, but they don't have limits so you can just use them every turn. Ergo there's no forcing a choice of 1 spell over another because you only have 4 focus left (or something like that). It's an ability and I choose to implement it. (See where I'm going?)
Lucitan is great in that you can make 3-5 different abilities to implement and use one of those for all jacks in your command range and make it so they don't count as being "hymned" so you can have a choir too. This can get OP'd really fast, but it'd be cool. Any new jack that comes out has to be careful that rules interactions don't make it like Rhyas and the Warchief, bouncing around at mat ~15+ pow ~28+ or some such nonsense.
Given all this, the so called "jack caster" would fail, imo, if it didn't have some way to buff all models in battlegroup via a spell. It should cost you something tactically to augment an entire battlegroup. And not just for 1 turn like Amon and his feat, which is great, but a 1 time use only. All of his jacks that he likes to have are focus starved.
I'd say try and steer clear of augmenting support. A support of a support makes for exponential increase as opposed to just multiplication. Otherwise he'd have to be a +1 to any buff he gives just to not make him insane coupled with the awesome support options we have. A +1 guy would be a yawn on paper. pSev already does that.
One thing: I am all for Elite Cadre [Choir] and making the song range their CMD rather than the 5". That would be sweet and not OP'd.