Brother tc215

Hello! 
My name is Philip im 15 years old and me and my brother who is 19 are currently in the progress of rebuilding and retrofitting a brother tc215 that hasnt been used in the past 15 or so years. It was real dirty when we bought the machine so we decided to take it apart, clean and paint everything. By now we have taken apart and put together the y and x axis. I also took apart and cleaned the ballscrew nut and the linear rail carriges ( the 15 yo dried grease was no fun ). We thought about reballing them but never got to it. If the backlash is bad we will probably do it then. So i have some questions, we will probably replace all of the axis motors and drives, they are very small 150 watt toshiba motor and 300w on z. Thinking of using
stepperonlines t6 series servos. 750w for x and y and 1kw for z. They are just rebranded leadshine motors which i have heard good things about ( and they are very cheap ). Then the spindle motor and driver i will keep for now and see if its power is enough. ive gotten the pinout to the drive and it looks simple enough.  The orientation seems to be abit tricky. The atc motor i will replace for a closed loop stepper or a integrated servo i have laying around so that will be very simple to drive. The servo motors are step/dir so im thinking the mesa 7i96s ( almost the only thing in stock in europe ) will be a good fit for my project. Will the 16mm ballscrew and 20mm thk rails be enough for milling in harder metals like stainless and so on. To get a bigger ballscrew should´nt be so bad but the rails im not to sure about. i guess we have to wait and see. Do you think the motors are oversized i have gotten mixed opinions i just dont want to get them and they then turn out to be to small. im probably going to start ordering some electronics some time next week when i have put together the z axis assembly.

Now please feel free to answer some questions, add some questions and share your concerns and opinions.

i will probably go for the bigger motors since i want to unlock more milling capabilities. When would the deformation happen, at high load or acceleration?
i dont really want to wait for the cards from the us and the 7i96s should have enough input/outputs and for the less important stuff like lighting, button etc i will use arduino for expansion. Yes it has the drum style atc with the mechanical drawbar.