Hey, I found 3 more shugenja spells in an unlikely place!
Weapons of Legacy has 3 Shugenja spells - Revitalize Least/Lesser/Greater Legacy, which let you use daily powers from your legacy item more often. Daily powers vary in effectiveness, capping at Time Stop 1/day.
Given that Legacy Champion has a better HD than Shugenja, and also a better attack progression, and a much better skills list, and the legacy items can provide a lot of utility for the shugenja, it seems that LC might actually be a solid Shugenja PrC, even with the loss of 2 CL's. Those CL's are partially made up for by the gain of an extra greater legacy (type g, which is ~7th level spells), as well as other greater legacies which are generally on par with 9th level spells.
That is assuming that LC doesn't advance PrCs, of course, in which case you'd advance the PrC that is advancing Shugenja casting instead.
Sample Build: Human Shugenja 5/Paragnostic Apostle 4/Sacred Exorcist 1/Legacy Champion 10