Sharpco,
You bring up several interesting issues. I will tell you the reason I use my Tormek instead of a Twice as Sharp for sharpening scissors. I have never sctually used a TAS, however, everything I know about it inficates that it it is a good unit. I have considered purchasing one. I have no doubt that I would like it. My reason for not purchasing one is cost. I am a hobby sharpener. I also sharpen on a volunteer basis for my grandchildren's school. The Tormek does a very adequate job for this. It may not do the job as quickly as a TAS, however, with my very low work volume, I am not pressed for time. Even if I was in business as a sharpener, I would have to consider very carefully if the number of scissors I needed to sharpen regularly would justify spending $400US compared with $50 for the scissors jig for the Tormek you already own.
The TAS is small enough that fitting it in your van would probably not be a problem. The dust might or might not be a problem for you. For occasional scissors, I would have a hard time in convincing myself that the $400 was cost effective. I leave it up to you to determine the volume level where it wiuld be cost effective for you.
As this is the Tormek forum, I do not want to get into a discussion about the Viel. I will say only that I thought the Viel would a useful adjunct for the Tormek for me. It has been that. The basic Viel costs around $100. I planned to use one of my three spare shop motors. That fid not work, so I purchased a motor. That brought my cost above $240. I decided to switch to a variable speed motor. The Viel has been a useful complement to my Tormek, a $400 complement. As a hobbiest, I like the tool. If I was running a cost effective business, I would have to think long and hard about such an investment.
Ken