You can create g2 characters just fine in CA4.
1. obtain a flash template and modify it
2. use puppet producer in flash to create your own from scratch.
3. obtain the white paper and accompanying excel spreadsheet with the names of all the body parts if you want to do it all from scratch without puppet producer.
4. Export the individual vector objects in swf forma. and just replace the sprites of an existing character.
5. Using the sprite replacement feature you can actually make vector based g3 character (just not the head due to bugs) But you can also mod any existing g2 character by simply replacing the individual sprites.
Caveats,
1. RL no longer publishes their G2 whitepaper.So you have to find the info online if you want to do it without the help of plugins.You will still need a program that can export as vector based swf files.
2. There is a huge bug in CA4 that kills your vector shapes if you try to configure them for Render Style. So any vector development you do with CA4, you will have to do without the render style feature.

Ibis Fernandez | (available for hire)
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Professional Animator, Filmmaker | Creator of the highest quality (modular) G2 rigs for cartoon animator and developer of Toon Titan and Puppet Producer
Author of Flash Animation and Cartooning: A Creative Guide
>>> be sure to check out http://toontitan.com for professional grade assets, templates, and custom tools for Cartoon Animator and more.