Servo-DRO advice sought

Dear Group

I am enquiring about servo systems.

I understand that commercial servo's are dc motors with a built in
encoder to keep track of shaft positioning.

I am looking at making a cheap solution for my home setup.

OK don't laugh.... well go on then .....

I was thinking of using components from cheap electric battery
operated screw drivers that employ sun gears to generate a fair
amount of torque to the shaft.

The encoder would be a digital dro ( the ones that are similar to
digital calipers but with mounting brackets) with an io connector.
(Any other idears welcome!)

The software I was looking at would be Linux EMC.

Ok ....
By having the encoders (DRO's) mounted directly to the x y and z axis
of the mill any movement would be recorded and relayed back to
emc ....... This would eliminate backlash issues as the physical
position of the table is taken as opposed to motor shaft position.

Could this work?
What problems would I encounter?

General thought's and advice very much appreciated.

Kind Regards

SG