Nothing to stop you doing this now.
withdraw from the Motability scheme and use your monthly payment to lease your own car, pay your own insurance and servicing.
best of luck being able to achieve the same level of car and spec.
a voucher covering three years pip payments does not work, as you have to be able to sign in to that, with no loss of pip, you are expecting someone to pay that advanced sum, where is the benefit to the taxpayer?