200 rpm straight to 4in wheels is only 41 in/sec (you’re like a turtle). Since you’re only using a 4 motor drive (I would recommend a 6 one), I would recommend 200 rpm geared up 72:48 on 4 in omnis (62.8 in/sec).
Also, since you’re rebuilding, I would recommend switching as many axles to screwjoints as possible. We did it and it and the driver likes it a lot more since it’s more responsive.