A list of TODO tasks sorted by priority if you are interested in improving 
MooseX::App

* Alias command names (Difficulty:Medium)
* Permute (Difficulty:Medium)
    * see Getopt::Long permute
    * "--attr val1 --attr val2" vs. "--attr val1 val2"
* Better support for Hashref attrs (Difficulty:Medium)
    * optionally use colons (or any other character) instead of equal signs 
      as key-value separators
    * allow to specify multiple pairs in one attribute. ie. instead of
      --hash key=value --hash anotherkey=anothervalue
      allow the following syntax
      --hash key=value anotherkey=anothervalue 
      also see permute
* Getopt::Long compatibility (Difficulty:Medium)
    * coordinates=f{2} - Accept multiple values per key (see permute)
    * ! - Negation
* Nested subcommands (Difficulty:Medium-Hard)
    * ie. "mycommand.pl some command" would translate to 
      "MyCommand::Some::Command"
    * How to distinguish between subcommands and positional params?
    * Make sure that help handles subcomands (ie. "mycommand.pl some help"
      returns a list of available subcommands for "some")
    * Make sure that the typo plugin handles subcommands
* Handle type constraint unions (Difficulty:Easy) 
    * generating description for attributes
* Better positional param detection (Difficulty:Medium)
* Term plugin (Difficulty:Easy)
    * History callbacks
* Bash completiton plugin (Difficulty:Easy-Medium)
    * Handle enum type constraints
    * Hide in help (?)
    * Hide bash completion from bash completion
* Documentation
    * General improvements
    * Extend tutorials
    * Clarify and highlight MooseX::App::Simple
    * Add recipes (aka Moose recipes)
* Better error messages on unrecognised params (Difficulty:Medium)
    * Improve "Did you mean ..." suggestions
    * Suggestions if attribute was supplied with only one leading dash
* Rework Testsuite (Difficulty:Medium)
    * Testsuite fixtures are currently a mess
* Allow alternative param/attribute syntax (Difficulty:Easy-Medium)
* I18N (Difficulty:Hard)
    * Based on current user locale
    * Register languages
    * Register strings (ie by plugins)
    * How to handle PODs?
    * Language fallbacks
    * Allow to specify command documentation in multiple languages
* Virtual attributes (Difficulty:Medium)
    * Handled via callbacks
    * Not sure if really needed - find workaround and add howto pod