I hate to argue with so much good experience from Buck.
He has helped me a lot.
But not sure i would start grinding with full width wheels, and all the experience and increased accuracy of the set up that implies or requires.
It will be slower, but if you grind with the edge of the wheel rather than the face, it will do quite a few parts before necessary to re-dress. Besides that, since you require less than .010 stock off, you can dress, set height, and walk away even on a 2 axis machine. It will grind to size and shut off. It will be difficult (after a little practice and benchmarking) to get a more accurate flat surface without a lot more experience. If it worries you starting out, make it a 2 pass op, one roughing and one finish @.0005 down, but should not be necessary at that increment and your specified part tolerance.
I am seriously leery of used machines*, especially ones scheduled for painting, but maybe that is just me. That said, I like my DoALL D1030. If you get a DoALL, get one with the cool-grind set up. This manual explains my method of grinding, page 2. Almost deep as you want. I sometimes even go .040 down, but i won't take .010 sideways, usually right around .005" per table reversal.
It's not as fast as Buck's method, but it is low stress for small machines & cost effective unless you are doing 100's of parts at a set up. Also the cool grind feature that is an option on DoALL machines, pages 12 - 14
* Used machines - need to clarify that - all my machines arrived used and sometimes abused.
My point is never trust a dealer unless you really know him personally, without doing your own inspections. Many dealers are honest, but many never actually inspected the machines they are selling. Or did not inspect them in a manner that matters to a critical user.
Which brings the old " grind 4 (or 5) blocks scheme in 4 corners & center of the chuck, to "prove" the machine ways are good. It does nothing of the sort. Buck's method of shimming a straight edge and checking both directions (or a small surface plate) is the only way.
However, since the chuck is ground with the machine itself, the chuck face will mirror the ways. If they are humped, so will the chuck face - BUT- it will be dead paralell (if ways are not so bad it's hopping). This means that it might well pass the 4 or 5 block test with flying colors.
The implication of that is, that a machine with poor ways and your fixture, might not grind all the parts flat or the same size. Putting them on a perfectly ground chuck, which mirrors the ways, will force them all to be the same size, and in a small area, you might not be able to measure or indicate on a surface plate, whether they are flat or not.
So, your fixture is really an elegant piece of toolmaking and workholding. If you put it on a less than perfect machine, you might or might not find some error in the parts. With your specified tolerance, it probably does not matter, but just one more way to think about geometry.