I agree completely that the Samurai should be revised, most likely by turning it into a cavalry unit.
It’s worth looking at what Petersen said about this a few decades back. In Ask Sandy XV, he openly acknowledges what folks have already been pointing out in this thread: “Specifically, we have noted that the mighty samurai is not especially useful in his main task of UU-killing.” He goes on to note that as a result, the team has “upped his movement speed a tad” and “increased his anti-UU damage”, i.e. they doubled down on the original design. This didn’t really work then – that’s why we’re having this conversation in the first place – and I don’t think that tripling down now would be the answer, either.
Elsewhere Petersen says that originally, the Samurai was supposed to be able to toggle between ranged and mêlée attacks (this possibility has already been mentioned at least once above, as far as I could see). Obviously such a change has been somewhat preempted by the introduction of the Ratha, but I think there’s still room for such a unit. The Ratha has 10 mêlée, 5 ranged attack – the revised Samurai could have, say, 9 and 6, respectively, augmenting its role as a cav archer. And/or, given that the naginata has been mentioned above, the Samurai’s mêlée attack could have range 1 like a Steppe Lancer. Lower HP, the retention of the Samurai’s current 1/1 base armor, a slightly higher speed (1.35, same as a Knight) could also set it apart. And to distinguish it more from other cav archers, it could cost food and gold instead of wood and gold, which would synergize nicely with the Japanese fishing bonus. (This largely excerpted from another post I made.)
A revised Samurai could also have a weakness against gunpowder units. In terms of the game’s continuing development, this would be a neat little homage to the unit’s former, unmounted version, and would also be another interesting mechanic cutting across usual counter- and counter-counter-lines (e.g. the Ghulam being strong against archers) since gunpowder is usually thought of as anti-infantry. It would also constitute a fitting nod to Kurosawa’s Seven Samurai, Yojimbo etc., where it’s usually gunpowder weaponry that overpowers the samurai protagonists (or at least seriously endangers them).
That’s just my two cents, though – plenty of other variations are possible, and I agree with a lot of what’s been said already (e.g. that there’s some awkwardness here since Japanese knights and especially cav archers presumably already represent samurai – onna-musha and naginata rider are both very cool ideas). I don’t see much potential for modest revisions, though – the Samurai shouldn’t deal anti-UU bonus damage and it shouldn’t be an infantry unit, either. A proper overhaul is in order.