DHCP reservations for a range of MAC addresses

The Microsoft DHCP server has no concept of a list of MAC addresses that are outside one of the configured DHCP scopes. I'm also not aware of any way to get the Microsoft DHCP server to return an IP address outside of the scope in which the DHCP relay agent's GIADDR address falls. I don't think you're going to be able to replicate what you had w/ the Microsoft DHCP Server.

As an aside: Before you consider handing-out IP addresses to public clients using a Microsoft DHCP server you may want to get a clear statement from Microsoft as to whether or not these devices need CALs. Microsoft has made contradictory statements about this. To be "safe" I always use a non-Microsoft DHCP server for public subnets.

Edit:

You're absolutely right that a DHCP superscope will allow IP addresses to be assigned to clients outside the subnet of the GIADDR that the relay agent passes. It's not a feature I've ever used in production but, even so, I feel like a bit of an ass for not thinking of it.

Static IPs are normally outside the pool range as you do not want static IPs assigned to other hosts. As long as the static IPs are in an IP range local (or relayed) to the DCHP server they can be served.

The leases file records which addresses from the pool have been assigned to a host and when that assignment expires. This is used to ensure that multiple hosts don't get assigned the same IP address. The presence of an active lease does not indicate that host is currently connected to the network. As static IP assignments are know by their definition, they do not need to be recorded in the lease file.

If the lease time is too long and clients frequently change, it is possible to run out of addresses while only a few hosts are currently connected. This is more likely in a hot-spot or guest network than a typical office network.