I entertained this same idea 5 yrs ago, IMO, an uphill battle.
1. Unless you receive the customers rifle and develop exclusively for it, precision may not be the exact wording. If you are just crafting ammo, basically one size fits all. No matter what you do, you are not unique.
2. Think of the number of reamers available for any case we shoot, neck dia, freebore, etc...
3. Component changes, any change on your end affects your buyers. If I had gotten into it, a contract would need signed. Figure a close rd count that the barrel may last. Buy that number of jump tolerant bullets, same number of brass, and enough powder, that all belongs to the customer, yet you store it. Yes, if you were part of the rifle from the start, maybe you could take return brass and reload it, but now time becomes a factor. Plus you may need the rifle back if adj are needed between new and fired brass. There are some givens in load development, still time consuming.
4. No matter what a customer wants, how well you think you know him, you can't send warm ammo out.
I can go on and on.
Example, last fall I met a guy on the range I shoot quite a bit. no reason for details, but I ended up helping him, tricks, ballistic solving, we started shooting together some. One day he breaks out a Bergara B14, 6 creed, shooting a factory offering real popular on this site. The rifle and ammo were impressive for factory. He struggled on a few targets, and he was shooting decent. I finally had him shoot 3 groups at 500 yards, all 3 were around .7 moa, give or take for 3 shot groups. So I asked, you want better, yes, so that day I took all his brass, he had 100 pcs fired and cleaned them, Next day, he came over and we processed brass, loaded up test rds with RL 16 and hybrids. That afternoon testing, he shot 3 groups that went under 1 1/2" at 500, we picked the one that held vertical best and now hits 5" plate to a grand, I will not load his ammo, he has to be part of it and it works.
The best way to lose customers is to fail them.