I put this up as a Cuusoo project since there hasn't been any professional fishing boat for minifigures, among the official Lego sets, ever! The closest thing to this was perhaps a certain sport fishing boat, set 4642-1.
This would be a medium size set with around 600 pieces. Estimated cost I guess would be around 40$, which I think would make it a great set.
There are some other fishing boats on Cuusoo already, both by the same author. One is a great micro scale fishing village with harbour and boats, the other one is conceptually speaking a minifig scale ship just like mine, but it is much much larger and does not include minifigures since it is a model of a real boat which disappeared, so the author has decided not to include any minifigures out of respect to that crew.
My set would include around two minifigures, which would be the minimal appropriate crew for a ship this small.
The color scheme of this boat could be varied according to what color people wish for the most.
Here is a conceptual image of how you would play with the trawl. The outliers, or what they are called, are lowered, and the trusses from the two small red winches are fastened onto them. The trawl is rolled out from the main winch, and the two net doors, as the brown things on the ends of the trusses from the two red winches are called, are fastened onto the net.
I hope I haven't misrepresented how trawl fishing works technically, I'm no expert on these things...
The trawl could be made from around four normal lego nets that are tied together. Thus no new parts are required to be made, even if the trawl presents something of a special case when it comes to new parts as it is not made of plastic and hence would not require any expensive new molds to be made.
As you see in the above picture, the roof comes off, to reveal the steering cabin, and a small crew area with a stove and a chair and a very small brown table.
Here the lid of the storage space is opened, to reveal, surprise surprise, loads of frozen fish. Also, the lid of the engine compartement has been lifted and the diesel engine can be seen.
Here you see the boat from its underside, and as you can see there are small bulbs which makes it possible to push the boat along on a surface without leaving ugly scraping marks; this is in order to increase playability.
I include the MLCad .mpd file for those who want to play around with that.