Then use Buttercup's wealth ability to create stuff on the other side.
That could well work for providing stocks at least.
You're either on board with the idea or you're not. The fun thing is getting it to work without just making up something out of left field. The theory is strange enough and secret enough and obscure enough that any GM could ignore it without comment.
But really the answer probably should come out of left field, if just a little bit.
When you just throw down, oh X in the form of Buttercup has power Y in the form of Astral Gateway so it can do Z in the form of basically a teleport, but at the same time lots of entities have that same power Y and they can not do this that creates the question of why? Because if AG is all you need, then you have to consider other spirits using it as well and all that implies. Or players who get control over a spirit with said power and how they may (mis)use this.
Maybe Buttercup uses an unique ritual or artefact (both of which plays well with the secrecy thing and also would make it much sought after if discovered) or maybe as she has grown as a free spirit racking up karma and now through the spirit equivalent of initiating she has developed a new spirit power that had the AG power as a pre-requisite to develop. So you can build on what she has and still explain why it is new and exciting without that disconnect.
So it's not so much whether we are on board or not as we have toyed with a few concepts to create a bridge between two points, but we are just asking for consistency in your fluff & crunch.
Unless you are planning to write for CGL, then writing contradictory material may be a bonus/
