Of course, one soldier on a fishing boat should not be able to capture a large warship. But 10 warriors on a merchant ship, capturing an empty ship (conditionally empty, i.e. without a garrison) with close contact - why not.
If, of course, the boat can swim close and stay afloat for some time without being sunk.
Very suddenly, one player's unprotected fleet (without a garrison) can be intercepted by an even weaker fleet (but with a large garrison) of another. In my opinion, this would be very interesting and generally corresponds to the historical outline, when ships were captured on board.
Note: That’s why I wrote the idea about a two- or three-fold advantage of units in the garrison of a ship going on board, so that it would not be one soldier, but several.
And of course, there must be technologies that improve boarding practices. For example, “grinding hooks on ropes”, which could significantly reduce the time required to capture a ship. And vice versa, the technology “high sides” and “military commandant” to reduce the possibility of boarding a ship (increases the time for interception) even if there is no garrison. And if there is a garrison on the ship, these technologies make it very difficult or almost impossible (as with towers).
Moreover, “high sides” are only for wood. And the “military commandant” technology is only for metal.
.....
But these are all dreams... dreams.
However, maybe the developers will really like it and do it?