I think both career skills fit better on footknight. The charge helps him very well in his tank role, he doesn’t have the sheer tankiness of unchained/zealot/ironbreaker, so he makes up for it in being able to CC. It also works well to aid teammates in need, charging straight through the enemies to rescue them. It looks a lot better for a fully armored knight to charge through enemies.
At the same time, an inspirational ability is more in line with being a knight than a mercenary.
Although one thing, mercenary also gets the increased attack speed for teammates, so in general he might be meant to be an inspiring figure as him.