Some issues with the Flash Bone Tool are described very well in this YouTube tutorial video (as well as his claim that there is an Actionscript solution). If you don't want to watch the entire 10 minute video, then at least watch the important part from 1:39 to 3:05.
In essence, one of the main issues with the current Flash Bone Tool is that you cannot swap symbols in the middle of a bone animation. I can easily imagine that some Actionscript inserted on a layer above the bone animation layer could actually force a symbol swap to occur, thus resolving the issue. This code may in fact be fairly simple, but would require the user to enter certain information into certain sections of the code (the name of the symbol which would replace the existing symbol, and on which frame or frames of the animation the user wanted the swap to occur). Because most animators don't want to spend the time putting in the code, and then digging through it to enter the symbol names in the right places, I think our plug-in would make this all a lot easier. The user would simply click on a "Bone Tool Helper" icon in the toolbar, and a window would pop up with empty fields which the user would populate with the required info.
I imagine our Plug-In would look something like the Plug-Ins offered here.
Those tools solve other issues that Flash has (not the Bone Tool issues). They have free trial editions (with limited functionality), and there is a charge for the "pro" versions.
I'm unfamiliar with programming this type of plug-in. How difficult would it be to build a production-ready, user-friendly plug-in as described? I'm looking for an assessment of feasibility and estimated level of effort for an individual with experience and knowledge with plug-ins and bones.