plominoagain , I'd hoped there might be views from serving officers. What you say I think is the biggest obstacle to tougher action. It would probably need new legislation to protect police from such repurcussions, and that needs to be weighed against concerns about police abusing their power.
Addressing other points.
"They can't". In my view, it's rather that they won't. plominoagain has given a good reason why. My belief is that in some circumstances forcefully stopping a suspect on a motorbike would be lawful. The ECHR/Human Rights Act includes exceptions for defence against unlawful violent and for making lawful arrests. I can't find any cases of police being tried for manslaughter or death by dangerous driving of the suspect in a pursuit.
At least one police force's guidelines (Cheshire) do state that police pursuit tactics, including 'tactical contact', "could be the best option for use against motorcycles which have been involved in very serious incidents and whose riders continue to threaten public safety and defy other efforts to stop them." So some police forces at least are prepared to consider it. But the legal uncertainty is leading to (what I consider excessive) caution.
Concerns of safety of bystanders. This applies to any police pursuit and police already consider it. I do not expect or wish that consideration to be reduce. I'm not sure there'd be that much difference whether the suspect is in a car on a motorcycle anyway; it's cars that are capable of more damage in a collision.
Tougher sentencing? Hmmm. I remember reading once that criminals are less deterred by a possible longer sentence, but rather more deterred by a greater risk of getting caught.
The Henry Hicks case, well there was more going on there that just pursuing a moped. I reckon the officers would be facing a hearing if the same circumstances had happened with Mr Hicks in a car (though I accept the circumstances would be much less likely to occur).
On a final note, maybe in 5 years time police cars will come with drones and all pursuits have air support. That should stop the suspects getting away.