Why 4 axis?I have worked with several types of tooling block to create moulds for carbon and glass and have used either 3 axis or 5 axis machines.Could you explain quite what configuration of a four axis machine will be able to rotate the workpiece once it approaches 3000mm in size?
Additional questions;do you have the knowledge to create your own 3D objects or will the files be supplied to you?Have you factored in the cost of a CAM program and almost certainly a custom post processor?
Until these things have been considered,you don't really need a wish list of machine components because a machine that can't be used by anybody without the dedicated software and without files of the objects to produce won't be very productive.
I wish you success with the project.