I have some ideas\predictions as for what Galio should get

W shouldn't work on minions. Perhaps a full on remake on the ability and give him a different, more interesting form of sustain or damage prevention, should still work on allies but not heal him if they get hit. That's like giving a child candy and taking it away. E shouldn't give a trail of MS, it should be a gap closer to line his ult up with but with obvious counterplay Q Is just down right awkward. Like Heimer's E before his gameplay rework, just needs to be modernized and do less damage while not being as expensive to use

R.. One of the best abilities in the game imo. Should be immune to CC during the channel but make the damage lower and have a bigger max stacks of increased damage for each time someone auto attacks him in the channel, less rewarding if used on single targets, more rewarding if catching multiple enemies with it.

As for his passive... I thought of the concept that is to drain power from attacks. For each time a magical ability hits him, he gains a charge and he discharges the stacks through auto attacking or as a bonus to his ult. It's really hard to properly describe it, I'm not quite sure how I can get this to work but maybe if you let this idea cook in your mind for a while you might get the hang of what I'm trying to present here.

It's not like I want to say Galio's body is made out of runes so he can absorb magic and laugh at Cassiopeia and Ryze