I think this is the right list to use, Jane! The reason for that is,
as others have suggested, this is not so much a rules as
Gloranthalogical question.
Mechanically, there is no reason why your Vingan could not have a
whole entourage of treetop-trotters, so long as she overcame that
multiple-target penalty and they were close to her when she invoked
the feat.
However, the contraints are more likely to be theological and
practical:
- Feats are about _becoming the god(dess)_ -- it is one thing to
bring ones junior sisters in Vinga along on a treetop jog. Indeed, I
could see it as the stuff of pre-initiation rite ('follow Vinga's
ways and just see what you can accomplish!') but the Vingan or her
devotee peers might be less comfortable with using it to boost a
bunch of hairy-bottomed Uroxi.
- And practical? Well, remember that a bad failure can harm the
devotee. This might be considered Vinga punishing her for trying to
use her magis on said Uroxi. And one entertainingly nasty point to
bear in mind: what happens to them if the caster dies or is knocked
unconscious? Were I a Lunar hunter-killer in that situation watching
the devotee cast her magics, as soon as everyone was nice and high
up, I'd make damn sure my commandoes did everything they could to
zap her and watch it rain Uroxi!
All the best
Mark