This requires extracting some files from war3.mpq. Open up war3.mpq in winMPQ or MPQview (find it on google if you dont have it). The files you are looking for have this format:
**UpgradeFunc.txt and **UpgradeStrings.txt
where ** is Human, Orc, Undead or NightElf.
All upgrade requirements are stored in the 'Func' file, so it is easy to change them.
Remember to import whatever file(s) you change back into your map (using winMPQ).
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.