Re: Neighbor may complain to the city, what to expect?
What you have there is a 'Karen' problem, nothing you can do will make her happy short of moving across the country. She already has a track record. She won't give up until she wins or is completely destroyed.
If she calls the city, they will most likely send out code enforcement to check things out. If code enforcement determines that there is a problem then work with them to mitigate any problem to their satisfaction, be advised that some level of environmental protection authority may get involved and this would not be good. If they don't see a problem, then destroy Karen's credibility by presenting the opportunity to goad her into calling the city when you are not cutting, or preferably not even in your shop, just make it look like you are in your shop. She can only cry wolf so many times before she is ignored.
Your propose filter system is a good idea, that should mitigate any smells coming from the process as well as removing any particulate from the vent system. Put a small windsock on your shop and only cut when you are downwind from Karen. This won't stop her from complaining, but it will prove that her complaints are unfounded. Video evidence is always a good thing. A camera in the shop and another with the windsock in the frame would go a long way to proving your position.
In this case having a LLC or as a sole proprietor makes no difference.
If you are in an agricultural/farm zone, start a pig farm and feed them restaurant food waste, that will mask any odors from your laser operation, and really give her something to complain about. Make sure your zoning allows something like a laser cutting operation (light industrial?), you may or may not be in compliance.
Best of luck.
Jim Dawson
Sandy, Oregon, USA