Tried asking the people who produce DD-WRT firmware? You won't get much support for that in an official Netgear community.
The chances that the C7000v2 will support alternative firmware are probably close to zero. Neither you nor Netgear have any control over the firmware on a cable modem/router. That is in the hands of the ISPs, and they are notoriously reluctant to roll out legitimate updates, let alone "pirate" firmware.
Finally, you have posted your message in the section of this community given over to Nighthawk WiFi Routers. (This is easily done, given Netgear's complicated community structure.)
Many questions apply to different types of device, so you might get responses here, but you might get more help, and find earlier questions and answers specific to your hardware, in the appropriate section for your device. That's probably here:
