All of these scenarios only tinker around the edges of the DT system, and as you you shown, will only have a minimal impact on who is on DT1.

The new DT system is such that those now on DT1 have slightly more influence/power as those who were previously on DT2 under the old system and those on DT2 under the new system have slightly less influence/power as they did under the old system.

I don't think it would be appropriate for a high activity requirement to be on DT1 as many people over the years have been able to show themselves to be trustworthy enough to be on DT (and understand the system) after being here for only several months. Perhaps a requirement to have 150, or 200 activity to be on DT1 would be appropriate, although I don't think it would affect who gets onto DT1 >99% of the time.  

IMO a better question that should be debated is if merit is an appropriate indicator for someone to be able to have influence on the trust system, and if it is appropriate for many people who do not trade (participate in the marketplace) to have an influence on the trust system (that is suppose to help those who do participate in the marketplace).