If T=3MB it's like a 6MB limit with pressure to keep blocks smaller than 3MB unless there are enough transactions paying fees so it's worth including them?
I think T should scale over time as bandwidth is growing. 42 transactions per second is still a low limit for a global payment network.
As far as I can see, and given that:
Obviously increasing the block size requires a hard fork, but the [penality] fee pool part could be accomplished purely with a soft fork.
Then it would be possible to raise the block size limit to 6, 20, 40, ... MB, but introduce a soft cap and a penality mechanism for "large" blocks. The penality function (and thus soft cap) may be freely adjusted over time, as long as the resulting block size doesn't exceed the hard limit.
The process will resemble climbing a hill rather than running into a brick wall.
Very well put, I like it.