Been looking to add biscuit to an order, but no one has had in in stock with the others I was looking for. Interested if the caramel helps turn the maple into a frosting taste.
(Like
@LittleBird said, FA Zeppola is gonna be popular with donut fans.)
The maple glaze on those store donuts looks like caramel, but that's just because the powdered sugar and milk makes it opaque. That kind of glaze uses lots of vanilla, too.
Percentages are just estimates, but I'd start with 3% Zeppola, 2% Vanilla Classic, 1% Vienna Cream, 1.5% Maple Syrup, all FA flavors. That may or may not be precisely what you want, but it'll be a vape-able, reasonable, maple-y start. If that's not enough Zeppola for the doughnut part, consider adding just 0.5% FA Cookie rather than more Zeppola. Over about 3% Zeppola and you'll taste cinnamon, especially as it ages a bit. A little TFA Brown Sugar could be a good addition, but look out for the DX (diketone-free) version of it, which has a stronger molasses-type flavor that could make maple taste a little weird.
A couple notes about FA Maple Syrup. If your bottle is very old, shake it & taste it before you start. When it gets old, it changes (not well!), loses its sweetness & will ruin everything it touches. Also - this flavoring leaves a strong maple-syrup-scented vapor trail. Vape it in the kitchen and someone will come looking for pancakes.