Reflexed risers are easy.
Since you're going to do the siyahs "under glass", the wood type isn't nearly as critical -- it really just folds the glass apart. Padauk is 'way too heavy for siyahs -- you want light and strong like Ash or even oak
I've made more than a dozen Asian style bows -- wood-glass composites, wood-wood composites and bamboo-wood composites, and almost always use Ash or Oak for the siyahs.
It's the direction of the grain run that's important; ideally curved grain following the curves of the siyahs.
You could lay up siyahs on a jig, using short lengths of "normal" bow laminations; cut them, shape them, and then add them to the rest of the glue-up. I've done that a few times. Won't work well with a modern, fancy pressure hose set-up because it requires two or more trips under pressure.