Wal now, BW...
To me, a true custom rifle is a rifle that is built (or rebuilt) to the customer's spec. Whatever it is that that means. If a customer is truly happy with a plastic stock, a trued up action, and a accurate barrel, that is custom just for him. To me it would be an action that I prefer (probably a Ruger #1 or Hagn) that has been worked over till its as good as it can possibly get, a barrel that has been milled down to include integral quarter rib for the rear sight, milled barrel band sling swivel and banded front sight. Fancy schmancy wood of marbled walnut, with shadow line cheekpiece, fit to the way I shoot and seemless with the action. Action probably be case colored and the barrel deep old world style of bluing. The trigger would be set for no discernible creep or overtravel and break like glass about 2.5 lbs. All this in whatever caliber cranks my engine at the time, which thinking right now, might be a 275 H&H Mag or 318 Westley Richards.
Having said all that, I'll go back and restate what I truly believe: It's a rifle that is built (or rebuilt) exactly to what the customer wants.
YJ