So basically you want to force everyone to customize their trust list instead of using the default list?
That is something already being considered by theymos:
I don't think doing such a thing will stop the trust farming by DT1 members. As long as you can gain positive trust by adding someone to your trust network, it will be abused.
Who on the DT1 is farming trust currently? IIRC there was a thread that reviewed that recently and a few people changed their lists?