Maven should add support for project local dependencies where a jar file is stored in one of the lib folders in the project.
Currently there is undocumented support for it using maven.jar.<id> however the use of <id> is deprecated and should be removed.
Another way I can think of is to use the properties project.path and local.path
project.path == dependency relative to the location of the project.xml file. This ensures that you are on the right file by using getParent of the project.getFile() method.
local.path == dependency wherever on the system (just like maven.jar)
This would help speed up migration of ant projects to maven projects.