THe snow load is not big deal, as all pre-engineered steel buildings can be designed for any snow load/wind load needed. But why go with 4:12 pitch? Most steel buildings are base priced at either 0.5:12 or 1:12 pitch, and anything steeper adds to the cost. Personally, I think that for a stitch down roof you need at least 1:12 for good drainage, and I used 2:12 on mine which looks and works great.
As for piers, it can be done, but you will need very large concrete piers of about a 1 to 1-1/2 yards of concrete for each of the main rafter columns. On a 60' building you will probably have two rafters at 20' on center, so that equals 4 piers. Generally these piers are poured as part of the foundation and have two rebars each that come out of the side of the pier into the floor slab, and are connected to the two rebars from the opposite side within the concrete floor itself. This ties the piers together from one side to the other. Since you can't do that without a floor, you will need larger and deeper piers to provide more stability and support.
The end wall columns are much smaller and don't need nearly as large of a support structure.
Also, stay away from General Steel. They are just a jobber/retailer and don't build any buildings themselves. I know they advertise a lot on the radio and in local newspapers, but BBB doesn't give them a good rating at all. Also, their sales people are on commission, as are most of the others as well, but their's seem to be pushier.
For that matter, almost all of the steel building dealers on the Internet are nothing but jobbers that sell buildings mfg at one of about 8 contract mfgs scattered around the country. Each dealer will claim that the address it is being shipped from, which is always different than the company's own address, is a mfg facility they own. But once you start checking you realize that a lot of the different companies are all shipping from the same locations, i.e. a contract mfg facility.
Several exceptions to the above are Nucor Steel Buildings, Varco Pruden and Butler I think has their own also.
In fact, there is nothing that would prevent you yourself from going into business, setting up an agreement with the contract mfgs and becoming a completely new building supplier. In fact, I really think that a lot of the companies are nothing more than an office with a few phones and a few sales people taking orders for another company to mfg and ship. All that's needed is a phone, a computer and the design software that allows the saleperson to plug in sizes, design specs, etc, and it will automatically calculate the materials needed and the costs.
