I would not be very keen on this one.
There is no existing standard OID that would cover this, which means Meraki would have to create a custom OID. Not only do you have the grief of having to use custom OID's on the SNMP manager side, it then means Meraki would be locked into supporting that OID.
At the moment Meraki can freely innovate the Wireless Health feature - being locked into support an OID would limit this.
You would be better off writing your own API to SNMP converter if you wanted more state exposed to an existing SNMP platform.