UK will have to accept EU migration and contribute to EU purse but doesn't have a seat at the table making the whole referendum a fruitless pursuit that cost the UK political clout.
Conversely the Germans may see Brexit as a threat to the EU (particularly if the UK does well outside the EU) and may veto the UK joining the EEA. The UK performing poorly outside the EU would act as a disincentive to other members who may be weighing up leaving.
Another alternative to the hard border between N.Ireland and Ireland is a hard border between N.Ireland and the rest of the UK. Though some saying having to use a passport to travel within your own country defeats the purpose of the country.