I don't think this would help him much, nor does it really matter as cc'ing Galio out of the ultimate should remain counterplay to this ability, otherwise its a get out of jail free card and incentivizes using the ult to run or to save the ult to become immune to crowd control.
Galio is extremely weak right now, honestly the worst I have ever seen him, but for other reasons; not being able to flash taunt, and his ultimate being virtually unusable in solo queue, as well as doing less damage than any of his other abilities... yet it still maintains an unbelievable 200s cooldown at rank 1 and a whopping 160 at rank 3....
I think a few things would make him better:
A. Taunt duration need to increase if he gets out fully charged W's, to account for how hard it is to pull off because he can no longer flash taunt which was his only redeeming quality.
B. Reduce all pieces of his ultimate timegates: The timer he takes to jump, the time he is in the air, and the time it takes to drop to the ground should all be reduced slightly for a faster cast. For a 200s cd ability that doesn't even give his target damage reduction anymore, it has no business taking 5ever to cast, doing next to no damage, and even the most immobile characters just waddle out of it. (For more reference Twisted Fate's ultimate is 180s cd even lower than Galio's for an infinitely better global, and the knockup of Galio's R is a measly 0.75 seconds when most are 1s, hell even Nautilus' point and click one knocks up for 1s. on a 120s cd)
C. For an anti-mage, not having a silence is almost criminal. I think he should get a silence in some manner, perhaps by hitting someone with the apex of Q silences the target for a duration, this would also help him get to his target before it inevitable dashes, flashes, or steroids away which is another weakness hurting him.