What you describe won't work. The import H.264 video feature is so that you can export animations that will be in time with the original video.
Importing an image sequence would work, but it wouldn't be any better than just doing an animated GIF.
What is the overall effect that you need, and does it have to work on mobile? You could for example import an FLV into a timeline, and export that as a single SWF file, but that would just work for desktop.
Can I export them as HTML 5 Canvas ? That’s what I need to do.