But first this is what AOP is all about, to not upset all the code that is already written and having to recompile it.
But it is two pronged in that, if you are going to create an aspect to remove your tangled code. Like you have security code all over the place and you want to remove all that code into an Aspect, then you will have to remove all that code that your have for security in your classes and write it once in an Aspect class. But in the long run it is really worth it to detangle all that code.
From logistics point of view, introducing AOP is quite easy (in fact, trivial if you are already using Spring). All it takes is some modifications to your build system.
