Actually, the "Baht run" can be done with full fare Y or J tickets almost as cheaply, and the M-class ticketing was not a major factor in ozplan's original scenario: 20% fare difference. The 100 segments can be done for about US$1,200 in business, since domestic tickets are so cheap. (That's the key to the whole thing.) So I don't think Thai can legitimately stop this mileage run loophole unless all their domestic tickets are excluded from STAR Alliance qualifying miles/segments qualification.

Your Toronto-London example requires discounted advance purchse tickets that would have to be "clustered", as you note, and would also only qualify for 250-miles each flight.

I suppose over the course of a year, one could fly almost each weekend back and forth and back and forth to accumulate 160 segments (YYZ-YXUtkt1/YXU-YYZtkt2 Saturday YYZ-YXUtkt2/YXU-YYZtkt1 onSunday) at the cost of C$6,080 plus taxes and other fees, but the Baht run would be cheaper. But this only yields 40K in qualifying miles.

In the end, Aeroplan requires too many segments to make this a realistic option.