Well, I ended up using Quartz as it is, through a JobDispatch.java which sets up the scheduler and so, as Quartz specs state, using all libraries from Quartz instead of Deltaspike scheduler module. So far so good, I thought I was totally independent from deltaspike-scheduler-module-api-1.2.1 and deltaspike-scheduler-module-impl-1.2.1, but, the thing is I wasn't. Once everything was working properly, I decided to clean up a little and get rid of those two libraries. I realized then that I had them in my buildpath, so that I removed them from there first, and finally deleted them from disk. For my surprise, when I tried to run my app again, some exceptions came up, NullPointerExceptions in fact, coming from the @Inject variables. I didn't research this deeper, but I let those libs live in the buildpath since it was working right that way.
My thoughts are that in some way, those libs keep the CDI alive through jobs, no matter if all the cronjobs stuff is taken from Quartz libs only.
If anyone can shed some light here, be welcome.
Thanks!
UPDATE 4/2016
Deltaspike 1.6 now supports this kind of functionality:
Configurable CRON expressions
UPDATE 2 - 4/2016
For Quartz cron expression, configuration is not so straightforward, check Configuration at container startup time for more information