You could modify the Crystal form to remove grouping by warehouse code, although I don't really recommend the practice you are using. If you NEVER have the possibility of adding additional warehouses, you might be ok, but I've learned over the years to never say never :)

Was there a particular reason you didn't decide to add UDFs to hold your additional Bin Locations instead? It would certainly be much cleaner, and allow for easier use and audit I would think.

If the sales order form prints on 1 page, you could make a new S/O form for printing picking sheets.

Make the S/O form look like a picking sheet.  This could be an easy solution, assuming the sales order form doesn't print separate pages for each warehouse.