The challenge is to be as adaptive as possible...
...Using one of thise other dedicated software not only limits a person but locks them into designing with just that software.
multiple options rule. Locked in doesn't. .
I would agree with all your points, except the assumption that anyone with a sign specific (do-it-all) software, would thereby limit themselves to attempting to do it all in that software.
Myself for an example, I was proficient in using Adobe software for many years before owning my company. At that point, I also had experience in multiple sign software packages. So as I built my business, I made use of a vinyl cutting software (Casmate) that I purchased second hand (with dongle) & which had several design features that Illustrator didn't do so well at that time, such as scanning access, bitmap tracing, efficient outlining tools & some envelope distortion tools. Still, there were several things I did in Illustrator or Photoshop as well.
Later, I received a crossgrade price to buy Flexi Pro for $1100, which I did because it did not require giving up Casmate. I continued to rely on Casmate & never began to learn Flexi until I bought my Mimaki printer. At that time, I was being offered Onyx or Wasatch, as tools I would need to have to run my printer. When my supplier learned that I owned Flexi Pro, although it had been sitting unused on the shelf for 3 years at that point, he observed that I didn't need to buy a $2K rip software after all.
Again, it is a tool that serves a purpose for me, but rastor design work is not the purpose it serves. I had been doing that in photoshop for over 10 years, so installing Flexi as a production manager tool for setting up & outputting my large format print/cut jobs worked good for me, but was no reason to quit using photoshop. I am working far more with files of my own creation, then from customer supplied files, so i am already in photoshop creating an image. The only bitmap editing tools I have ever had any desire to use in flexi is the crop tool, and that worked just fine the one time I needed it in the last 3 years.