That's an interesting tactical change, however, it also cuts the distance infantry and cavalry has to cover to close in with the artillery pieces, making them even more vulnerable. Have you considered simply increasing round shot range instead of reducing other ranges? Or sharing that 50 difference between them, making the ranges 425 and 375?
Problem with increasing range is that you then encounter the problem of foot and horse artillery being able to fire on opposing player in 1v1 maps especially as soon as deployment has ended hence why I do not really want to do that.