All-lane running is the reverse: the hard shoulder is completely missing and you have to just hope that if you break down and can't make it to a refuge bay that a camera operator notices your car stationary in the lane, which is still going at full speed, and closes the lane before someone hits it.
In personal experience of coming up on stopped cars in live lanes, with no signed warning of any kind, they aren't noticed immediately. A stationary vehicle in a lane comes appears very quickly when the lane is moving at 55-70mph.
Typically (here in Italy) the normal lanes are 3.25 to 3.75 meters wide while the emergency lane is 2.50 to 3.00 (it depends on the period the highway was built, I believe)
So you need to change horizontal lines/signage and make all lanes, including the hard shoulder/emergency lane, the same width, and this means that in "normal" operation travel lanes will be narrower.
On paper, sure.
In practice it's the worlds best passing lane because the drivers who make the left lane useless as a passing lane don't self select to use a lane that's narrower than the rest, has a ton of merging traffic and a barrier on the harder to see side of the vehicle.
Smart motorways are unpopular because they typically include a lot of speed enforcement cameras and lower speed limits, so you can no longer zig zag through traffic at 90 miles an hour.
Thus, smart motorways, pollution enforcement zones, and neighbourhood traffic charging schemes are very controversial. The same people who got exercised about face masks will cross the country to protest them.
These people are the base of the current government, which needs a culture war as the real issues look unwinnable right now so the civil service are under pressure to find a reason to roll this stuff back.