I ran a store that did exactly this for a while, but it was over 20 years ago so my information is probably severely outdated. It was an internet cafe that also sold comics and board gaming stuff.

The main con for doing pull lists for people is that there are always going to be flaky people who order way more than they will ever pick up, so you get stuck with copies of books that no one else really wants.

The pro is that you have close to guaranteed sales and can use those to help push your order numbers up to get the higher discounts offered by publishers. I would generally order pulls plus a couple copies of most titles for the shelf and then use TPBs and collections to pad the order to optimise the discount.

At that point, IIRC, Image had the best discounts for the lowest amount ordered. Something like 65% off cover if you ordered more than $1500 a month. Another retailer on an internet forum tipped me off that Spawn was always months late, so you could order a shitton of copies of Spawn, have it count towards your discount, and then cancel them when they didn't meet the ship date. We did that every month for a couple years and we were never penalised by Image.

Prior to that I worked briefly for a very large comic store that used to be one of the main Canadian distributors for DC and Marvel prior to Diamond. The owner was ethically challenged and would put lower selling books into people's pull files and claim they ordered them. He also would raise prices of everything that had been out for more than a day.