an idea for dynamicFlow alternative

Here's an idea for saving dynamicFlow in DFXP/TTML--  could we consider the use of SmilText and SMIL's TextMotion module (http://www.w3.org/TR/SMIL3/smil-text.html#SMILtextNS-TextMotion) as a way to implement roll-up captions?  I read the SMIL 3.0 implementation report and I see that there are already two implementations of the scroll/crawl features:  see http://www.w3.org/2007/SMIL30/SMIL30-implementation-result.html.  Is there any way to use this to salvage, or even replace, dynamicFlow?

Geoff/NCAM