I think it is pretty clear this is a bad idea.
The trust system is designed to be a way to determine the appropriateness it is to trust someone else with your money/property. By limiting the default depth to 1, you put the burden of this determination focused into a very small group of people. Additionally, since the majority of trust ratings are in reference to a completed trade, very few people would be affirmatively show as being trustworthy enough to send funds first to.
As mentioned by blazedout419, the default trust system is most import to be enabled by default for new users. It allows new users to conduct due diligence on their potential trading partners.
Granted, maybe users should be "forced" to create their own trust list after a certain amount of time, however many people choose to not use a custom list because well, they agree for the most part that people in default trust should have their ratings counted. If people were forced to create a custom trust list, say once they become a full member, then I would say that most people would make one that mirrors that of default trust, however they would likely not keep it updated for when people scam, start to send crazy trust reports, ect. which would probably not be a good thing. Additionally the people who do currently use custom trust lists generally add people who are in the default trust network, which should say something about how well the default trust system is working.
If you have enough negative trust from people in your trust network so that they show up as having a "trade with caution" tag, then you should well trade with caution because enough people whose opinions you trust enough for you to view them by default thinks they are a scammer. By making the warning toned down as you request means that more people are going to get scammed after they have received warnings that a scam attempt is highly likely by the person in question.
I consider this request to be an attempt to make it easier for people to scam in the future and as a result I consider you to likely be someone who will try to scam in the future.
I was almost tempted to reply to your thoughts here, but given the fact that you're currently on a troll tspacepilot kick (see his last posts, everyone), I think I'm just gonna leave this as is. But hey, ACCTSeller, sounds like you ought to give me negative trust for this, right? What's holding you back?
I did give you negative trust for this, right after I wrote that post.
If you are unable/unwilling to counter my arguments then I think you should admit they are valid and admit the suggestions in the OP are nothing more then to make it easier for people to scam.
P.S. I thought I was on your ignore list