Ok, no replies so far, but I managed to work my way around it.
Like always, some time in the docs, plus double that amout of time of trial&error usually solves these kind of troubles... ;-)
I now deploy all 3pp's separately as jars, and can now see them in the UnfiedRepository3 mbean. (That particular bean is very helpful in these cases).
enable loadtime weaving (turned on verbose)
spring.jar, x.jar ... -> deploy
myApp.aop -> deploy (aspects classes and META-INF/jboss-aop.xml)
myApp.war -> deploy (servlet, views, spring beans & spring xml)
when I first visit my jsp's I get A LOT of loadtime info from the aop-enabled classloader.
Then it works, my spring beans are intercepted by JBoss aop framework.