Caporegime
In addition your solution is still limited by your boiler capacity and ability to heat the water, if you have a pants boiler or a god awful combi your warerflow might be better but the temp less than a high power electric shower.
Balls. Almost every conceivable combi supplies hot water at a far faster rate than even the best electric shower. And if you have a hot water cylinder being pumped to the shower head, this will still provide a far more awesome experience than any electric shower.
The only conceivable advantage is reliability, but people seem to magically forget that you can get power cuts as well as boiler break downs. In fact in my experience the former is more likely if anything.