Static IPs Reservations ISP

I work for an ISP. I want to see if there is a more effective way to accomplish static IP reservation for customers. Currently we assign a /29 or a /30 to our static IP customers. I build a VLAN between our core router and their ONT. Their gateway resides on our core router. I am wondering if there is a more effective way to accomplish this than to build out a VLAN for every customer that wants a static IP address. Our DHCP customers have their own VLAN. My understanding is that you don't want your DHCP and static IP customers on the same VLAN is because someone could manually assign themselves a static IP address of a customer who is suppose to have that IP address reserved.