JOSbcc,
You appear to be talking about a Double Disk Grinding machine with some type of Ferris Wheel or Elevator type of loading fixture to securely hold groups of parts as they pass between the Wheels. This would require rather large diameter wheels and would be great for automating the operation.
The Thrufeed System as applied to double disk grinding, which you mentioned earlier as a take-off of O.D. Thrufeed Centerless Grinding, would be difficult to implement due to the tendency of the parts to rotate as well as tip unless you kept heavy continuous pressure on the in-going parts as well as the out-going ground pieces. IMHO, This would be a high scrap process.
Another option, for smaller production quantities, would be to clamp a stack of the pieces in a ratchet type fixture which allows the two opposing sides to be simultaneously ground on a Straddle Grinder. The Stack of parts would then need to be indexed 90 degrees with the Ratchet mechanism to grind the other 2 opposing sides. The Tolerences required would dictate the design of the fixture. Having extra Fixtures would allow the parts to be pre-loaded into the fixtures so that down-time would be minimized. Advantage would be smaller diameter wheels and lower cost machines and fixturing.
If you decide to perform either of these operations and are wanting to do large quantities, Structured Porosity Vitrified Bond Diamond Wheels would be very effective for this type of operation and cut your wheel maintanance, trueing, dressing costs.
Hope this helps.
RamingtonStall