I’ve looked into some papers and found more evidence that binders may not be necessary at all. Here’s what I’ve learned, but feel free to correct.
Nanocellulose fibers tend to irriversibly agglomerate and form additional hydrogen bonds with neighbouring fibers when drying, resulting in plastic-like material (hornification) but with less/no elastic properties.
This might be the reason why bacterial leather cracks and becomes so brittle over time or when exposed to sun (and thus dry). The agglomeration is something that is probably less desireable when the goal is to mix the fibers into composites. However, the hardening of the material may be desireable when you use it as the main material where ceramic materials are used or where elasticity and impact absorption are not really important.
I could conclude that a first drying step may not be necessary, unless for storing it to accumulate a large stock of raw but less qualitative material. This means that for small objects, a SCOBY-smoothie or semi-dried SCOBY would work even better.
Nanocellulose is also very hydrophillic, which explains why it tends to dry at a rather slow rate.
I found most of these insights referenced here, though still looking to read the original sources: