Griffon supported this feature until 0.9.5, but we had to remove it because it turned out to be a source of headaches. Instead, we made sure that snapshot plugins are easier to work with. In-place plugins in Grails work fine because all Grails plugins are distributed natively, which means that they will compile at the same time that the application sources are compiled.
Griffon otoh plugins are distributed in binary form, so you might think it would be easier to work with this function, but no; for starters with transitive dependencies of PITA; Then you must ensure that the plugins are compiled in the correct order with their own dependencies in isolation (this does not happen in Grails!).
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