The legal process can always be refined and improved. It has gone down badly lately that defendants have refused to appear.
For many years, British sentencing was based on rehabilitative principles (hence why for example Colin Pitchfork who raped and murdered two children and sought to evade conviction was released) and more recently has (in my view thankfully) e.g. applied longer sentences for murder, introduced the whole life sentence, etc to tip the balance away from convicted criminals and more in favour of the victims and their families.
A change to the court practice so that a failure to appear for sentencing means at least, say, an extra six months, or, for a whole life sentence, later consideration for “enhanced” status when behind bars, would be welcome, in my opinion, and I am guessing is under consideration.