Currently, mojo configuration is done externally to the container, in the
  DefaultPluginManager in the maven-core API. In order to get from here to
  there, we need to do several things to add capability to the default
  configuration of plexus. This document will detail those changes.

Container Enhancements

* ExpressionEvaluator

  Currently, the expression evaluator used to resolve configuration values

    /**
     * Enables/disables network access to remote repositories.
     *
     * @param offline {@code true} to disable remote access, {@code false} to allow network access.
     * @return This request, never {@code null}.
     */
    MetadataResolutionRequest setOffline(boolean offline);

    /**
     * Gets the artifact to resolve metadata for.
     *
     * @return The artifact to resolve metadata for or {@code null} if not set.

/**
 * A request to resolve the dependencies of a project.
 *
 */
public interface DependencyResolutionRequest {

    /**
     * Gets the project to resolve dependencies for.
     *
     * @return The project to resolve dependencies for or {@code null} if not set.
     */
    MavenProject getMavenProject();

    /**
     * Sets the project to resolve dependencies for.
     *

    }

    /**
     * Get the absolute path to the private key file.
     *
     * @return absolute path to private key
     */
    public String getPrivateKey() {
        return privateKey;
    }

    /**
     * Set the absolute path to private key file.
     *
     * @param privateKey path to private key in local file system
     */

 implement it and then I disappeared for 8 months so it never came to pass.

 So I guess it's important to figure out what people are using properties
 files for and see if we can't incorporate it all into the POM. Or if we do
 have properties file (something I would like to avoid) say they don't
 contribute in any meaningful way to information in the POM. For example a

/**
 *
 * Note: uses @Typed to limit the types it is available for injection to just ModelProcessor.
 *
 * This is because the ModelProcessor interface extends ModelLocator and ModelReader. If we
 * made this component available under all its interfaces then it could end up being injected
 * into itself leading to a stack overflow.
 *
 * A side effect of using @Typed is that it translates to explicit bindings in the container.

         * to new fixed version, or by dropping plugin use from currently built project.
         * <p>
         * Note: if a reactor build contains a plugin (with issues) and later that built plugin is used in build,
         * it will be reported as "external". It is up to developer to correctly interpret output (GAV) of issues
         * and realize that in this case he wears two hats:" "user" and "(plugin) developer".
         */

@REM
@REM Environment Variable Prerequisites
@REM
@REM   JAVA_HOME         (Optional) Points to a Java installation.
@REM   MAVEN_ARGS        (Optional) Arguments passed to Maven before CLI arguments.
@REM   MAVEN_BATCH_ECHO  (Optional) Set to 'on' to enable the echoing of the batch commands.
@REM   MAVEN_BATCH_PAUSE (Optional) set to 'on' to wait for a key stroke before ending.

    /**
     * Interpolates expressions in the specified model. Note that implementations are free to either interpolate the
     * provided model directly or to create a clone of the model and interpolate the clone. Callers should always use
     * the returned model and must not rely on the input model being updated.
     *
     * @param model The model to interpolate, must not be {@code null}.

    /**
     * Builds the projects for the specified POM files and optionally their children.
     *
     * @param pomFiles The POM files to build, must not be {@code null}.
     * @param recursive {@code true} to recursively build submodules referenced by the POM files, {@code false} to
     *            build only the specified POM files.