You are right to be considering all the implications of having a lot more torque and power in a TDI.
There has been a fair bit of discussion about DMFs on the Octavia II sub-forum of Briskoda. IIRC the Sachs version sounds like it might be better than whatever brand VAG have been using on their 1.9 TDIs in particular (it seems like it is almost designed to fail after a certain amount of use).
The T5 sub-forum of the Brickyard also has a couple of recent tales of woe regarding DMFs and gearboxes.
One of the problems with replacing the DMF with a single mass flywheel is that all the power pulsations will then go straight to the gearbox and the rest of the drivetrain, which may be even worse over the long term (DMF's being usually cheaper than gearboxes).