Garen. Redefine him as the champion who will always be ready to fight at any stage of the game.
Passive - Mostly the same (Superior healing when out of battle)
Q - Target an enemy champion. After a short delay (say, half a second), Garen charges a fixed distance to that champion's position. Minions are knocked aside (automatically triggers minion aggro). If Garen makes contact with any champion during his charge, he comes to a stop, crashing into the enemy champion and stunning them for a short duration.
W - Garen raises his sword into a defensive position for a short amount of time. During this time, Garen takes decreased percentage damage from all sources in front of him.
E - After Garen has been in battle for x seconds, you may activate this ability. Garen pauses for a moment as his sword shines brightly before he swings his sword in a wide arc in front of him. Any champions hit get knocked back (enough to disengage any melee fight).
R - Mostly the same. However, it is instead now calculated based on the difference between Garen's current health to his target's current health (similar execution style ultimate, while also promoting Garen to be building tanky and utilizing his W and passive abilities)
Riot wanted to buff Garen's passive because they feel that's something Garen should have. Why not accept this 100% of the way, and turn him into an engage/disengage fighter who revels in short, bursty fights, before disengaging and healing up, and charge into battle once his health is back.