The unreleased miniatures ones do look good, but other comments I found about them also note how small they are which is a shame. Also though nicer than the GW ones they are amazingly more expensive.
I think the best conversions I have seen are these:
From the Michael Hanns blog, They use bits from the Morgul Knights (which I do like) on the Dunharrow bodies.
I want to keep the Jackson/GW style rather than a more accurate look because I already have so many of the rest of the range. My thought at the moment is to do something with the plastic Easterlings.