Cool idea! I have worked on her A.I. a bit and I can give you some insight.
The current version of Sparky needs to be taught how to use each card individually. We've done some work this year to make this easier, and more robust, so we could better make the Color Challenge games - but adding new cards to her decks usually involves a bit of work. This mostly revolves around telling her what are the legal targets. The bigger problem for your suggested feature: there are a lot of cards we don't use because she has no idea how to use them.
I would like to have the ability to "test" a limited deck against her. Especially, if I'm working with a wonky mana base. I've seen a few threads asking for that so I put it on our backlog. It will have to be costed and prioritized with everything else, but I hope it's simple to add. If it does get implemented, more than likely, Sparky will just be using her normal 60 card decks.
Hopefully, that answers your question!