One way would be to make a "super" faction for yourself. You can go to Glest > techs > magitech > factions, and copy whichever faction you want to modify. Rename the copy to "magic_super" or something like that. Then go into magic_super and change the magic.xml to magic_super.xml. Open it and change the starting resources and starting units to whatever you want. Now when you start a game, pick magic_super as your faction and you'll have whatever starting resources and units that you specified. That should be a lot simpler than modifying the individual unit xml files, but can give you a big head start.
The absolute simplest way, however, would be to use the pause feature. You can pause the game, look around to see what's going on, and issue commands. Then when you unpause, your units immediately try to execute those commands, so it basically makes your reaction time super fast.