I see lots of people have looked at this, but no replys...
As far as practical, I think all the ways you can do it are pretty rough. There are several copies of adjusted databases out there that have some prestige classes added. I think they can all be accessed from EnWorld's E-Tools page. But then, you have a hacked databases, and you can't be sure of the consequences. There is a legendary PATCH 1.0 coming out at some point in the as yet undetermined future which might addresss some of these issues. Also, the creator of the E-Tools Helper (Davin, I think) apparently has plans to create something that will allow adding prestige classes, but last I saw he was waiting on the mystic PATCH from fluid. So for now, E-Tools is not really all that great for Prestige Classes, although I use it quite a bit for other things, like making my own monsters and drawing up quick regular NPC's, but I DM a campaign. BTW, most of my DM buddies don't PrC's very often when creating NPC's because it's too much of a pain in the a$$. Gives me an idea for a thread...