Purely speculative, but I think if swabs remain an issue for too long, alternatives could start coming online, such as even using qtips + saline (no idea if it works, it's just an example). The current swab + Universal / Viral Transport Medium combo is optimized for flexibility; it is designed to work across a very broad range of viruses and bacteria that have different viral loads and shedding characteristics. The current pandemic is pretty much COVID-19 only, so I think it's a priori feasible that a specimen collection procedure can be found that uses common materials. We did try early on to see if saline or other buffers affected the performance of the assay, and it worked fine in those conditions.

We use fairly standard chemicals. I haven't heard from our suppliers about shortages for the chemicals we use. Chemicals and enzymes tend to be relatively fast to scale up for bulk manufacturing.

There's always manufacturing risk that a product will not work as expected. In fact, the first COVID-19 test developed by the CDC did not work as expected, and this delayed testing by several weeks. We de-risk this as much as possible by performing experiments as early as possible, akin to the fail fast mentality of checking for the highest risk failure modes first. Since we don't have a national healthcare system in the US, the manufacturer takes on the vast majority of the risk of a defective product.