Destroying the car (or at least the engine) isn't entirely out of the question, as that has successfully happened when incentives are given, such as with the cash for clunkers program. But I can't imagine that would be a better option emissions-wise compared to EV conversions.
Perhaps subsidizing EV conversions could be a viable route. A significant tax break and perhaps government loans for newly formed conversion companies could really ramp up scale of conversions, and hopefully lower costs.
Ideally, even larger tax breaks could be offered to worker coop conversion shops to encourage that form of business.
Since these won't perform as well as a purpose built EV, as another user mentioned, owners will likely want larger batteries to compensate. If done at scale with lithium based batteries, that would be both costly, and worse, terrible for the environment due to the requirements for lithium.
Sodium ion batteries are just about production ready, and would be the environmental material of choice if this were to be done, even if their range would be lowered due to the decreased energy density.
I can only assume the english translations are licensed differently? Are you able to watch documentaries from the German DW channel, DW Doku? Unfortunately I don't see the baobab documentary there. :(