I’ve stopped using this approach and let me tell you why:
1. Flash CS5 will have a way better editor (this is just for the reference, as I will most likely code in flash builder even after CS5 will be released)
2. Flash builder 4 (ex flex builder) will be tightly integrated with Flash CS5, no more need for this hack, even if you still want to code in flash builder.

These are of course things to keep in mind for the future, what about now ?

At the moment, having had a Flex 3 license, I’ve entered the beta program for flash builder 4 (beta 2 now). I’m pleased to say that until now I’ve found minor issues with beta 2 that didnt stop me from using it for production coding. So what I did is ditch this aproach in favor of a more simplistic to set up aproach using the “Actionscript Project” wizard in flash builder 4. These are the things to keep in mind(if you find this useful, I’ll write another post on how to deal with all the aspects):

1. Flash builder 4 will compile the project for you using the mxml compiler (compc if doing swces). If properly set up the project will not use the RSL flex libraries so the code will have no performance/size hit.
2. Assets will have to be imported from previously created SWCs
3. You CAN use all the features of the flex/flash builder including code navigation, automatic building and on spot error/warning hinting.
4. Because of 3 and the fact that once you export all your assets and set up the project, you will not use flash cs4 again, the whole workflow is much faster.
5. You CAN have a flash builder project and flash cs4 project(.fla) using the same code/assets. So if you have to ship the flash CS4 project to your customer he doesnt even have to know that you coded it with flash builder.

I highly recommend forgetting about this post and following this comment.
Bogdan.

if you have an idea, i don’t know Ant very much.

Thanks,