I am looking to assign all our workstations a specific private IP
( via DHCP and register them w/ a DynamicDNS domain
(trusted.net). Any foreign workstations/Wi-Fi points/laptops would
be assigned addresses via DHCP, but in a different subnet
and DynamicDNS domain (untrusted.net).

There should be a way to implement this simple IF NOT .. THEN strategy
VLANS or other network equipment config.

Giving each MAC address a DHCP assigned IP from the trusted subnet
work, but is there any easier way?

Is there a way to bulk copy from MS DHCP server the MAC addresses?

Is there any way to have them still renew? Then I can expire systems
are surplused/replaced and reassign their IPs.

Thanks in advance!