Use the tribute code to send invisible items to the client to correct HP/Mana/Stats to the values you want.
All tributes are, are items that are equipped invisibly in 4 slots. You can hijack this code, and while losing the tribute feature, you gain the ability to do what you want. Look at the revisions for tribute.cpp to see an example we tried. (PEQ reverted it because of a conflict with the playerbase, but they balanced hp/mana/end throughout clients.)
Here's the revision in specific:
http://code.google.com/p/projecteqem...svn1888&r=1508