All cycles to be registered (reg plate) and be subject to a fit for purpose inspection same as other road vehicles.
Cyclists to have mandatory 3rd party insurance.
While both of the above may appear positive changes in the absence of human inertia, I believe that both would discourage potential new cyclists from entering the fray. I may be wrong.
However, I cannot think of a single instance in my 40+years of cycling and 30+ of driving when a road user has bemoaned the lack of cycle registration or cycle insurance - or indeed claimed that an issue they faced would have been solved by either measure.
I'm sure many road users can think of such an issue, but I can't.
All my children started to ride on the roads (accompanied) when they were about seven. How would I get insurance for an unguided seven-year-old missile on Her Majesty's Highway?
For all that, I think it would be good if the Police were empowered to confiscate any cycles they came across on the road that failed to conform to a set list of measures of mechanical readiness and in-place safety equipment. Not an annual MoT test... Just a published list of required condition and the authority to remove from the road any cycles that failed to conform.
However, if we added something like that to the list, then either absence of Hi-Viz or my choice of the dining-room wallpaper would have to go.