Guys I got some interview with some fishermen there, and they know nothing, how much naval architectural design has evolved. The trawler are rocky as hell. here is the map where, Indian, Bangladesh, Myanmar, all use same kind of boats, even worst, boat for offshore fishing operation. Kind of sad though. Am trying motivate them its time to change.
What follows is based more on advise picked up on how to sell something to a customer rather than actual design suggestions.
I think you may ultimately accomplish more by working the angle that new designs will make them more money, enable them to get to the fish faster and then to market faster. Possibly also save on the operating expenses at the same time from lowered fuel use.
You might also employ (some sample designs for styling as discussed below in hand) a really nifty idea like that that John DeLorean used to help create the Ford Mustang: asking fishermen that if their neighbor got one of these new style boats, what do they think would make it cooler, something really neat.
By this I'm referencing something discovered after they built the Edsel: when they asked people what THEY would want people responded with what was respectable and conservative, though laden with gadgets, and the Edsel resulted; but, when DeLorean asked what would be neat if their neighbor got it respondents were freer in their responses, less staid and predictable, actually indicated what they might want without it being respectable and conservative ... because in their mind they were putting themselves in their neighbor's shoes ... and the result was the Mustang. How this might work for you is rather than respond that this is the boat I want because it's like the boat I've got those you question might appraise the designs without that bias because you aren't asking them about their boat, but a neighbor's if they got one of these.
Take something like a Bolger Advanced Fisherman or a design of your own preference as a starting point and style it to give genuine homage to their beloved boats (several different versions might help). Maybe even modify it to handle the fishing tackle as they are used to if that doesn't undermine other goals you've expressed. Find out what the fishermen might think would be a sweet ride "if it was their neighbor's boat". Then sell just a few owners needing a new boat on the thought that this will make them more money that a new old-style boat.
You might at a later stage before boats are built invite a prospective owner to sail on some other modern boat of similar specifications elsewhere as observers and "honored guests" (catch more flies with honey than vinegar), let them see other fishermen take advantage of the benefits you say will help them make money.
These fishermen may be simple folk, but that doesn't mean they aren't savvy. Especially if you choose your would be first owners carefully: looking for someone who is hungrier than the rest. Once they succeed those new style boats could start looking a lot better to their neighbors.