Yes, it would be possible to build a txt2mobi command that do something like this. But in mobi2mobi I did not want to touch the content data at all.
But a better approach seems to be to use some external program like
http://txt2html.sourceforge.net/
to make a html file from a text file and then run mobigen or html2mobi on the html file.
Here is a Windows program for converting text to html:
http://www.softpedia.com/get/Interne...onverter.shtml