Hi bboklewski,
See my responses below:
1. I'm an ISP, I have single connection with customer. Customer needs more IP addresses. I just create a static: "ip route 63.250.250.32 255.255.255.224 <you side of p2p>" I probably already have a redistribution policy for statics, I just add that into my prefix list and its goes up. You your main site router, you just need to add routing toward your tenant's next hops. Otherwise, if you use BGP, then you announce this new prefix like any other prefix...and insure you have routing toward your tenant's devices.
2. Yes. You need 4 VLANs if you need segmentation between tenants. What happens when your tenants need more IP addresses? If your ISP gives you IP space, then they do the static routing as outlined in 1. You then add a secondary IP address on your main site router's interface facing the tenants--the tenants deal with further routing. If you get your own IP space, then same thing applies, except with a BGP configuration as outlined in 1.
HTH
Rate if helpful