It would be a good addition to extend the pattern API to support quantifiers known from regular expressions (e.g. Kleene star, ?, +, or count bounds). This would considerably enrich the set of supported patterns.
Implementing the count bounds could be done by unrolling the pattern state. In order to support the Kleene star operator, the NFACompiler has to be extended to insert epsilon-transition between a Kleene start state and the succeeding pattern state. In order to support ?, one could insert two paths from the preceding state, one which accepts the event and another which directly goes into the next pattern state.