Is there such a thing as a camelhair canvas tape? Like a banrol or other waistband stiffener but not fusible?
No idea. I could be made by cutting strips of canvas. BTW, that's I how I make my waistband interlining, with a strip of chest canvas and a strip of linen canvas. I cut the strips myself, but it is also possible to have this made in some places.
I've seen rolls of waistband stiffener, but those were cuts on the bias in a kind of canvas very different from what I use (sometimes even synthetic fiber).
Also has anyone heard of a jacket construction that uses both a fusible and stitched-in canvas at the same time?
Half-canvased / semi-traditional : as explained by SG, the front is entirely fused, then a canvas is put in the chest and lapel area. The only difference with the standard fused construction (which has a "floating chest piece" as say the marketors) is that the chest piece has the underliying body canvas part that extends into the lapel, so that it can be padstitch in order to get a nice lapel roll.
Now, something different : today, some cloths are made with the fused construction in mind, and have a pretty bad behavior when they don't have fusing. If you have to work with those, you need to fuse at least the lapel facing and the topcollar. It is usually a good idea to fuse the whole front as well, and then later put in a traditionnal canvas.
It looks like it is a step more, but it actually saves a lot of time since fused cloth is way easier to handle than unfused one.
Fusing the front has a definite impact on confort, since the cloth will breathe much less, and feel stiffer. So I consider this should only be done for cloth that can't be worked without it. But I can understand why some low-price ranges would do it for all cloth, since it give confort for the tailor to work faster with a nicer-looking result.
For real bespoke work on quality cloth, this should not be necessary.
Pad-stitching the lapel by hand when you fuse the front is just a way to say you don't have the machine to do it (it is expensive). Making silk finishing by hand is a way to get a nicer look (for people who like hand stitches), it doesn't change the construction of the coat nor its confort. And if you want a swelled edge, either you do it by hand or you have the specific machine to do it.