I hope it good enough to let us skip making early road and just pull the cart through terrain without slop.
Could be really interesting and fits the game really well. Passive bonus could include faster travel and increased carry weight with both foot and vehicles (and talents to specialize water or land vehicles). Also less calories to pick up and move stuff (if a calory cost is put on stock handling in the future to avoid stockpile teleportation method) and to swim. For recipes, I suggest giving them all the economical stations crafting, like Mint and Currency Exchange, Shopping Cart, maybe Treasury, some Offices... More stations could be created for them : Stock Exchange where sell and buy orders could be made for a product and target price, Auction table for putting auctions on items working like an election with people propose their prices until the timer ends. Some modern research could also use or require merchant work. XP would be gained for trade volume, distance traveled, stock weight moved. I would also like a talent to have a minor tax sales cut, would encourage people to try this career.
Have it so that the level bonuses for Merchant include increasing tax discounts (all the way up to exemption) from taxes levied by the three levels of government. Have it so the bonuses apply only when trading outside your home town, to encourage global trade.
DadSpeed server did this pretty well. They had a government tax break for people without any skills that functioned as haulers between everyone else that were doing their regular jobs and putting everything on the market.
I personally think these benefits should be added onto Shipwright, even if it's a bit of a clashing theme of overland/oversea travel. Shipwright doesn't quite do enough on its own, but would be well-rounded if it was given a more general "Transporter" paint job.
This could be in a career with gatherer maybe - give people increased foot or vehicle speeds with lower calories. Maybe there would be reduced or no penalty for going off-road and cross country. Vehicles driven by this class could be more efficient in consumption of fuel and maybe have increased storage slots or weight limits?
As someone who is perfectly comfortable with just transporting product, yes please. This would pair nicely with an early profession for road making. Getting tired of dragging a cart along dirt? time to make a road.