Boots of Swiftness Idea.

Boots of Swiftness have been nerfed into the ground essentially. They're only marginally 'more swift' than Merc Treads.

However, what if Riot were to add a passive to them that gave the wearer a movement speed increase in Bursts after running long enough or an activated burst of speed: either method using a set cooldown.

It would keep them "Swift" without completely stomping out other boots and making Boots of Mobility irrelevant for sustained movement speed.