Do you think it would make sense to allow people to buy beyond the limit (whatever the limited number of packs available to buy is) but for a higher price? So if they want to buy more than the limited number of packs available for sell, they can do so at a higher price and the difference from $2 goes to burning SPS. This way if they want to buy more packs faster, they can do it for more money BUT at the same time they help the entire game so nobody should be unhappy.
The biggest ICO was that of EOS ($4 billion) and they sold a certain amount per day for a year and allowed buyers to basically buy it through a daily auction. Maybe some lessons can be learned from that.