ok so with no frame in the intended stallion there's absolutely no chance of a lethal white foal, but I think I will test her to be safe... eventually. Just in case something else crops up as a possible sire for her future baby that does have a chance of having frame, like a QH or Paint [I like the stock type/TB cross, got a friend who has one that can jump the moon].
Regarding Agouti, the stallion I intend for her is chestnut, so the only colour possibility for the foal is chestnut [being that Magic, being chestnut, has to be ee, and the stallion also has to be ee], with varying amounts of bling depending on what white genes it does or does not inherit from its parents. But if I'm testing her for frame, I might as well test her for Agouti, to see if there is any possibility I might get a black foal out of her if I bred her to a different stallion. I like black ponies. I also like chestnuts, and bays, so regardless I'd be happy.
So the ermine marks are likely to be some other white suppression gene in play? Sabino and splash are both definitely present in the Thoroughbred breed yet we don't see many loudly marked TB's, so there has to be some gene or another that suppresses the white on them... right? [to clarify, I class frame as both white suppressive, and white causing, because it wants to keep the legs coloured]
This breeding idea I'm flinging around won't be happening for a few years yet, I really don't need a green horse to train up AND a foal to handle! Plus Her Highness has to prove herself worthy first... only reason I'm even considering it is because other than her neck and the angle of her humerus I quite like how she's built. Her feet are tiny at the moment but hey, she's a baby, there's time yet for them to get bigger.