Some of the modern-ish centerless grinding machines seem fantastically complicated to me and are based around high through put and automation.
Cameraman
I think you really need to get into a C'less shop and ask if they'd let you look at a setup.
Like Ox said, for an experienced guy, creeping-up on a dimension is pretty easy on a C'less, and once set it is pretty darn stable.
As far as automation for a few thousand pieces, how' bout a clapped out vibratory bowl feeder to present the incoming pins onto an angle iron, and then a long wooden dowel
to push them between the grinding and regulating wheel by hand?
I don't know much about setting up a centerless, but have watched a few setups.
With a properly trued up regulating wheel, dressed grinding wheel and correct support height setting ( all these are on the expertise of the operator ), they are one of the simplest
looking machines with deadly accuracy!
For short-length through feed work like what the OP is asking about, I don't believe my go-to shop has ever lost a single piece.
For full bar lengths, the only issue I've ever had is when he didn't take the time to set-up the input-output support rails and the bar ends were slightly
over/under size due to whipping.
Grinding to a shoulder ( plunge ) is where things seem to get trickier with certain part geometries, but even then I prefer to have the centerless shop tell me to F-off first
before sending stuff to a cylindrical grinder.