Right! Go ahead and make the tincture using the dried now (use both Echinacea purpurea & angustifolia root, and seeds or flowers, too), then use THAT tincture as all (or part) of the alcohol for a new tincture when you get in the fresh purpurea root from Pacific.
I've always made ours with fresh purpurea root and dried angustifolia root...but I talked to a gal one that used all dried (and used ALL the plant parts...including seeds & dried flowers and dried roots) and she indicated that hers was great!
Don't forget the "swell factor" when adding alcohol. Dried echinacea root swells SUBSTANTIALLY when the alcohol is added :)