Glad to see you using such an ace tool (as you know I'm definitely an advocate)!

With quite a few of your methods, you can use inbuilt functionality within Phing, which allows you to use the built in PHP functionality of Phing, rather than using it as just a wrapper for execs.

For others it's definitely worth checking the built in tasks, especially if they're not a full on command line buff =)

http://www.phing.info/docs/guide/stable/chapters/appendixes/AppendixB-CoreTasks.html
http://www.phing.info/docs/guide/stable/chapters/appendixes/AppendixC-OptionalTasks.html

Dom