If online businesses are required to collect state sales taxes and the small merchants are correct that this is too complicated for them to handle, I wonder if PayPal or banks will sell a service to small merchants that collects and pays the taxes for them. The merchant would have to funnel all online payments through the provider of that service before the merchant got his share. It seems to me that there would be nothing illegal about providing such a service.
Another alternative would be for small merchants to cease to be independent sellers and only be sellers on sites like Amazon or Ebay, which may do the tax collection.