I'm probably the one on the board who's come closest to filling such a demand, and I doubt I could or would do it again.
Several years ago, I was able to tap into a large supply of once fired police range .223Rem brass. I invested in the extra tool head, automatic case trimmer, and a ton of spare time.
Fortunately, the vast majority of the brass was Winchester. For consistancy, I would sort by headstamp the brass, and only processed the Winchester.
I'd clean the cases in walnut media overnight, retumble in fresh corncob to remove the dust, then lube the cases with Dillon spray lube.
I'd then run the cases through the 1050 using the carbide sizing die, adjusted with thier headspace guage. The cases were also primer pocket swaged, and trimmed with the Dillon trimmer, set to just barely size the neck only.
Then the cases went back into the corn cob media for a few hours to eliminate the lube and to knock off any remaining burrs from the case mouth.
Finally, the cases made a second pass through the press with an undersized Lee collet die to open up the case mouth from being sized again in the trimmer, and to clear any media from the primer pocket.
Things were fine when I used up my supply of Winchester brass. While I would pull one round per bin and double check the case in the Dillon headspacing guage, once set, the press never neaded any adjustment.
And then the supply dried up, and I began using Federal and Federal NT brass. Holy sheep dip, what a nightmare. Dies that produced perfect cases with Winchester brass, would produce Federal cases that fell below the minimum line on the guage.
Keep in mind, all this was just processing brass, not loading ammo. Having this much variability between brass types would seriously discourage me from any attempt to reload mixed brass.
I don't thing reloading commercially could possibly pay enough to make the labour worth while.