What would be some alternatives to excluding evidence that has been illegally seized?

The most likely alternative to the exclusionary rule would
be to make police officers who violate the 4th Amendment liable to be sued by the
defendants whose rights they violated.  In this scenario, the evidence seized in an
illegal search would still be admitted during the trial.  Afterwards, however, the
defendant would be allowed to sue the police officer.

A
second alternative would be to expose offending officers to internal discipline.  In
such a scenario, officers who broke the rules regarding searches and seizures would be
disciplined by being suspended or reprimanded.

Neither of
these seems likely to be effective, however.  The likelihood of a jury awarding
significant damages to a convicted criminal in a case of illegal search and seizure
seems extremely low.  So does the likelihood of police departments severely disciplining
officers for getting evidence that leads to a conviction.