Time to revamp traffic patterns at non-towered airports?

The FAA is expecting to publish its final rule covering Light Sport
Aircraft, Sport Pilots, and the training and repair requirements
sometime this year. I'm wondering what impact this rule will have on
traffic pattern operations at non-towered airports.

Most non-towered airports have a single traffic pattern that all
aircraft share. Some airports specify different altitudes for
different types of aircraft, but they all end up using the same
rectangular traffic pattern. In the current environment, this seems to
work. I think the reason that it works is because the greatest speed
differential likely to be encountered is a factor of two. By this, I
mean a typical non-towered airport has training aircraft that fly
approaches as slow as about 55 knots. At the upper end are twin-engine
aircraft that may fly as fast as 120 knots. The difference is about a
factor of two.

With the introduction of sport aircraft, many of which fly at approach
speeds well below 55 knots, I'm wondering how they should be
integrated into the traffic pattern. One option would be to have them
use the same pattern every other single-engine aircraft uses (but
perhaps at a lower altitude?). However, this will just increase the
speed differential encountered in the pattern, perhaps as high as a
factor of three or four. This can't be a good idea. Imagine trying to
merge onto the highway if traffic had speed differentials of four
times (operating between 30 and 120 m.p.h.).

Advisory Circular 90-66A provides guidelines for traffic patterns by
ultralight operators at non-towered airports. One suggestion is to use
a traffic pattern that is lower than the single-engine traffic pattern
and inside of it. Would this be the best option for sport aircraft? It
eliminates conflicts in the downwind and base leg, but there is still
a possibility of a conflict on final.

What's the best way to reduce traffic pattern risk when there is a
wide range in approach speeds – vertical separation for different user
groups, or a different pattern for different user groups? Or are the
current traffic pattern practices at non-towered airports archaic and
need to be completely revamped?