It actually would be more complicated than you think.
This is Ben's cup-o-tea, but I'll explain it best I can.
The list you're downloading isn't just a giant txt file. It WAS a giant txt file, but the server chops it up and separates each table. (which i believe are all separate files) The server does this...oh...about every 30 seconds, and that's just for PartyPoker.
It would technically be possible to get the raw txt and do all of that server work on the client, but then our bandwidth would get sucked up about 10x the speed it used to, more CPU load on the client end, we'd have to worry about offering tech support for this function, etc etc.
Unfortunately, a 100% client side version is not high on our priority list. I hope some day we're reputable enough to put your mind at ease...or that someone comes in and verifies that nothing wrong is going on in our software.
I completely understand your concern, I just wish I had some way to prove that we arent up to no-good
If you do work up the nerve to give it a try, come on back with any questions/critiques you may have.
Thanks,
-Dan