Minato can already move his hand fast enough to throw a kunai over ays head while he's moving full speed. Not only did Minato do that in base, he did it on his first meeting with ay with little info on Ays speed. Not to mention minato accomplished that from a mere distance of like 10m :|.
Now he has the added perception and sensory enhancement of sage mode. In addition to x3 the distance of their first exchange, giving him plenty more time to react.
Someone explain to me why on earth he'd need FTG. Minato literally replicates sm naruto vs 3rd raikage. Expcept even worse, because minatos reactions and speed are far better, and no need to waste time creating clones for the rasengan either. The toads arent even needed, this is over the minute Ay charges in.