I disgaree with this.
First of all, the archer problem should be solved with pathfinding. And the swordsman line shouldn’t counter archers. With extra pierce armor there would be no doubt they are very strong against archers.
The extra attack would help in many things. They would be radically better versus knights, the competitor melee unit. While knights should counter archers, the swordsmanline could be used well against knights, with the current supply tech+better pathfinding, it is really possible to swarm the enemy. You could say that there is already a counter for cavalry, the spearman line, why would I use them instead of swordsmen, pikes are much cheaper, have the same speed and deal better damage (against cavalry). The answer is that while pikes are a defensive unit, the long-swordsmen are offensive ones. With decent amount of damage against buildings (factoring in the +1 attack), they could actually force fights that are advantageous for the infantry player, unlike with pikemen. Note that one long-swordsman costs 45 food and 20 gold with supplies while a knight costs 60 food 75 gold, and you can even mix in some pikes for help, since you must hvae enough barracks.
Currently both cavalry and archers counter infantry, and archers and cavalry are pretty even against each other. I think this is not fair for infantry. I see this being fixed mostly by pathfinding, since that would help infantry in both against cavalry and archers, while it will help cavalry against archers. With good pathfinding, archers will still be superior versus infantry, if the player can micro, while they will be inferior versus cavalry, and infantry and cavalry would be pretty even (with supplies, a very underrated tech). To achieve the rock paper scissors gamestate, infantry should counter cavalry. And I completely see this being achieved by giving more attack to infantry, so with an increased damage they can force fights, and will also put up a much better fight against cavalry (+1 attack can even increase damage output by 20%, assuming knights and infatry players both teched into armor)
Summing up I think the infantry problem should be mainly fixed with improved pathfinding, but I don’t see why +1 attack would be a bad buff, even after better pathfinding (and it is also a really good buff before pathfinding gets fixed)
Supplies cost -25 food
Long-swordsman +1 attack
Two-handed swordsman +1 attack
Champion research time -10 seconds, upgrade cost -100 food (FU champion stats won’t change)
I would be really thankful to the devs if they could implement this, infantrys’ weakness is a long time discussed problem, and many players are bored of seeing only knights and crossbowmen in teamgames (look at recent BoA2 tournament), it is also disappointing that civilizations that have infantry bonuses usually tech into other units (for example vikings, malay and japanese archers, slav knights are much more often seen than infantry)
EDIT: long-swordsman and two-handed swordsman bonus damage versus eagles probably should be reduced by 1, if this balance change happens