This my way or the highway approach within maven sucks. It did not use
to be this way. :(
Use a single source directory, but configure 2 executions of the
compiler plugin taking advantage of includes/excludes to define what
to compile targeting 1.6 and 1.4. The issue here is that this is not
good fit for IDEs.
Have you tried this approach? I guess from a maven point of view it
should be quite easy. Note sure how the IDE will behave. Do you have any
Three modules might be more transparent for beginners, but as you say it
seems to be overhead.