Golf blu motion(?) auto I had as a hire car had it. Absolutely appalling idea, when it comes to a driving experience.
Its not quick enough. With stop start on, you want to pull away, press the gas pedal, nothing, it's busy turning the engine on. ...THEN your allowed go pull away.
With SS off you want to pull away, press the gas pedal, nothing, it's got a built in pause for when it wants to start the engine. ...so you still can't pull away when you want.
Infuriating idea.
The Golf one seems to possibly work off vacume pressure from the brake servo, so it seas a drop in pressure as you gradually release the brake pedal pressure, and starts the engine, so you can be ready to pull away, but It still lags. Rubbish!
Anyway, to retro fit, you'd need to insure the starter didn't engage under load as you pull away, or it will brake sumat. I suppose there in lies the problem...?