Using CNC as DRO to save $$$

In the name of conserving $$$ to be used on needed tooling, I am
trying to save the expense of a DRO. While I now realize how
valuable they are (just tried milling a slot in a 2" thick CRS plate
without one...yikes, keeping track of rotations to tell me how far I
have moved drove me nuts), I was thinking that since I am planning on
converting my Bridgeport Series I to CNC(I have the Servos, Amp's,
encoders and Turbocadcam, need power supply and controller...still
working on electronics, plan on talking with Jon Elson again when I
get up to speed..just trying to understand what I am buying before I
buy it as well as understand how to hook everything up), can't I use
the CNC display on my computer screen as a DRO??? The GUI I have
seen (MACH I comes to mind, but I could be wrong) shows what looks
just like a DRO display.

Immediate questions would be 1) Can I still operate it manually and
get a display 2) If yes, can I still compensate for backlash (still
have ACME screw until I can afford the G for ball screws. 3) Any
other issues that my newbeeness has overlooked?

Thanks very much for any help.

John