You can't quite use smart filters to initiate transactions in this way. But you could set things up so that mining permissions are always granted for a limited number of blocks, perhaps a week's worth, and that in order to be granted such permissions, an address needs to prove it has a certain balance of the native currency in the same transaction's inputs. A smart filter could be used to apply all these rules.
The alternative would be to add a new MultiChain feature which requires a certain minimum native currency balance (or ranking of balance could be better, to prevent a situation where no miners qualify) in order to allow an address to perform mining. Please get in touch if this may be relevant for you.
