I do not think a distribution can/should be started and declared a "main"
free distribution. Such a thing may happen though. For instance someone who
wants to create a free distribution for different needs (or simply having a
different vision of what are the best desktop applications) can take Trisquel
as a base. When it started, Ubuntu did not really aimed to be the base for
derived distributions.
Anyway, looking at the current 100% free distributions, such a main
distribution would not decrease the amount of duplicate work (which I still
believe is not a significant problem anyway): Trisquel is based on Ubuntu,
Parabola is based on Arch, gNewSense is based on Debian, BLAG is based on
Fedora and the remaining distributions do not seem to be based on any major
distribution.
In other words, developers disagree on what is a good base. Just pick Debian
(resp. Arch) as a base and try convincing Parabola's (resp. Trisquel's)
developers to base their distribution on it! The same would happen with a
100% free Debian-like (resp. Arch-like) distribution.
So, to answer your question:
1. yes, the current situation is a mess but...
2. ...no, developers prefer this mess to a common base that would be imposed
to them (they would simply stop working on GNU/Linux distributions).
