I'd say that the idea to 'downgrade' people into being bridges is a good one, if done without requiring user input. 'Everyone run a relay' might only be useful because so many of the people we say it to have fast connections. It seems reasonable to filter out persistently low connections (and allow them back in if their connection speed improves). That is not to say that every potential bridge should actually be accepted as a bridge. The 28B/s bridge is nuts - either it's on an embedded device or their torrc is misconfigured.
What I usually recommend is to users is based on their bandwidth and how frequently their IP changes. If their connection is fast and their IP never changes (eg, a desktop or server), then run a non-exit relay [2]. For a laptop that moves to-from work, then a relay or bridge. If it moves a *lot*, use Cupcake (which is a wrapper for flashproxy). Running a relay on a raspi or a router (?!) is not a great idea -- though people attempt both. If things could gracefully switch from being a relay to a bridge based on their speed, then that would actually make it more straightforward for users because they don't have to worry about whether they should be a bridge or relay.
People can't really estimate their own bandwidth without something like NDT, but they have an idea of how fast it is. eg, this connection is 21Mb/s up, 6mb/s down, but that's mostly irrelevant because my perception of it is that it's Fast. That perception would be the same if I were getting 2Mbp/s up/down. So maybe one non-technical change we can make is to user education and website documentation -- run a relay if you have a Fast connection.
Filtering people out based on advertised bandwidth is tricky - advertised bandwidth is only useful if it's based on reality. 250kb/s seems like a reasonable floor for both relays and bridges. 100kb/s is kind of the sanity check for a distributed bridge - if it's below that, it's not useful enough IMO.
The real questions for me are: how much of a gain is possible? and what is the right balance between number of relays and speed of those relays? and I suspect that until something is tried, it may just be speculation.
best, Griffin
[2] No one should be running an exit from home, and no one who is asking me about this at an event should be running an exit.