I think a grace period might be appropriate.
I will read you a quote from a Canadian Tax Foundation article that came out a few days ago. Talking about the situation in the Netherlands, the author said this:
[Netherlands] announced that bearer shares would have to be traded through a bank or investment firm, thereby removing their holders' anonymity and eliminating the incentive to use the shares for fraudulent purposes. Furthermore, shareholders were given a two-year period to register their shares with an intermediary designated by the corporation.
And further:
At the expiry of the two-year period, the shares will be cancelled and corporations will have to pay the value of the cancelled shares into a deposit fund monitored by the Ministry of Finance. Therefore, shareholders who want to redeem the value of their shares will have to report to the Ministry of Finance.
Having such a grace period would be a good idea to ease the transition.