I suggest adding the option for attaching subnet(s) (e.g., /29) of IPv4 addresses. Here are the reasons:
1. The current system limit additional IP (v4) addresses to a maximum 2 per VPS instance.
2. Networking will be much easier if you can obtain a bunch of IPv4 in the *same* subnet rather than randomly assigned ones, especially when you try to assign static public IPv4s to multiple devices (e.g., through a single VPN gateway.)
3. Other hosting providers are offering similar options.