I decided to hunt up information about the director and animation director for 5Ds, and came up a rather interesting find. Katsumi Ono, who did the storyboard (I don't know for which episodes, but I'm going to guess he did the entire storyboard) for first series is the director for 5Ds.
Explains why Ushio is there...
As for the animation director, it looks like he was the one who stuck around for Battle City. I don't remember if his animation was any good, but his main episodes were 74-90-96-102-108, and possibly more.
I don't want to go check myself on the animation quality.
The guy who did the mecha design did the animation check and key animation for Eyeshield21, and I'm hoping a certain person starting with "I" in their username comes up and checks the quality on that part. >_>