@Vilmos, Interesting, it sounds like AX tasks then typically run on an island (or within AX only) and that there is also heavy user interaction. I believe since this is a new implementation the client is looking to see if they can continue to use only one automation system. For example, they may have a job flow that consists of: a Mainframe job -> SAP job -> (some other 3rd party or home grown app), and may want to launch a batch job in AX afterwards (this is purely hypothetical). In this case it is better to trigger externally, as opposed to a manual task, or based on time.
The additional value is simply having all of your automation managed under one tool, and the flexibility and control an actual automation tool has. If AX tasks are only running within themselves, and requires significant overhead, it is probably not worth it.
@Martin, I appreciate the advice although it was probably the most condescending thing I've read in a while. But it does seem to agree with my conclusion that AX stuff is basically an island. I guess my next question would be then, if you had to implement a custom service, would you also HAVE to disable the scheduling services for all other possible batch jobs. That seems a bit strange.