Is hard to say what design pattern you should use without knowing what problem you actually trying to solve. However I can give you an idea about your application�s architecture: use Spring as the lightweight container and Quartz as the scheduler and you�ll be able to schedule tasks without running any piece of code. Almost everything could be done through configurations only (no need to use unix crons, Quartz resembles the same syntax).
Second use dependency injection to develop your beans (pojos) and if you follow the ioc paradigm closely with little effort you should be able to deliver testable and easy to maintain code (please notice that there is always a difference between designing a class and designing a testable class). And because you like using design patterns remember about the strategy design pattern (when develop your pojos).
Third use jMock and jUnit in order to fully test and cover your code. For running coverage reports on your code you could use either clover or cobertura. If you apply the strategy design pattern to your pojos you should be able to "inject" mock objects at runtime in order to build test cases that don�t really depend upon any external systems.
Fourth enable PMD and checkstyle when writing code in order to deliver high quality code.
This is probably a lot of work to do but at the end you�ll feel like doing the right things right.