Bad idea abandoning the hard shoulder, a largely continuous layby for breakdowns and a way in for emergency services. Sure four lanes might get more traffic through than three but I'd rather have the hard shoulder. Scary Mway driving without one.
For a long time there were holdups on the M6 and M5 (heading down to Sidmouth say) as 'smart Mways' were installed. However on the M5 traffic still stops dead all lanes for no reason and the now operational so called 'smart Mway' gives no warning or instruction.