A last concern is one that was touched on before, but not heavily discussed. This system would not be difficult to manipulate, but it would be much more difficult to detect manipulation. One could quietly buy up a lot of accounts then buy a 2nd set of accounts they want to be trusted. The first set of accounts could all have the 2nd set of accounts added to their trust list which would result in them being often suggested for newer users to add to their trust list. More experienced users may not even notice when this is happening because they are not being asked to add new users to their trust list.
To clarify, under the current system if someone wants to purchase an account on default trust list, they need to invest (and risk) a lot of money they will potentially lose if they are caught scamming. They will get one chance before they are called out as a scammer and likely removed from default trust list. Under the proposed system the initial investment would likely be somewhat higher however you would have many more chances to attempt to pull off a scam as the incremental cost to scam with a 2nd account would be very low.
Additionally it would be easy for the seller to keep track of what a default trust list account is doing under the current system while under the new system this would not be possible.