i have bought my share of equipment, (and possibly someone else's too)
i know when i buy equipment that there are imperfections, especially if someone owned it before you.
i weight the asking price, the availability, the scope of work i'm intending to do with the piece, and the return on investment.
if you are trying to do precision work (sub.001") you are going to need to spend either a lot of time, or a lot of money - maybe both brother .
i'm not trying to exclude unicorns that pop up. i captured a couple of them- but they are hard to find.
the single most important thing i can think of in your situation is to eliminate the carriage rise.
if you could somehow limit the clearance to a thousandth or so, that would improve the function
as a suggestion, mill off .007"(or .006" and hand file, lap, and finish as necessary) from the attachment side of the plate to make a step.
the end result is the untouched wear portion of the plate will still have the same wear pattern, without the excessive clearance.
then make a simple test bar and do the 2 collar test, that will tell you what it actually cuts like (in the 2 zones)
IMO, i would get another lathe before i'd get the bed reground.
you'll end up spending twice as much (time and money)rebuilding a machine than if you were to go ahead and bite the bullet for something superior.