You could always use the crypto currency as the store of value there, just as people did with MPesa. You don't necessarily ever have to convert it to a local currency.
MPesa doesn't store your money in some kind of private currency with a fluctuating value. If you're thinking of it as storing "minutes" as some American cellphone providers would, that's not right.
You deposit and withdraw Kenyan Shillings, or your local equivalent, just as if it were a shilling-denominated bank account.
You deposit and withdraw Kenyan Shillings, or your local equivalent, just as if it were a shilling-denominated bank account.