I actually wouldnt embark on a large scale character animation process in flash alone.
You need to look at this from a time persective.
Animation takes a very long time so think smart and save time.
there was a bones based flash animation package called MOHO by lostmarble.com
alas they went the way of the DODO.
2d bone based vector animation. very cool!
google has ghost images of what it looked like.
http://images.google.com.au/images?hl=en&safe=off&q=moho&btnG=Search&sa=N&tab=wi
If you can find a 3d package that you like and can render swf files or bitmaps.
you will eliminate a million different frames you will have to draw.
seriously.
creating your model in 3d will allow you to place and rotate while animating, to produce a series of cells for each fram eof each animation at each angle with each item etc....
imagine a character rotating 9 positions
now imagine him falling down in 9 positions
now imagine him attacking in 9 positions
now spells
now new armour
we already have 45 cells in 2d to render.
with a 3d object you just rotate the already created model saving whale meters of time.
