Well then, I have a working solution for DD-WRT to random cycle through sixteen consecutive addresses. The only disadvantage that it uses NVRAM, which is actually a part of a system flash chip, overwriting it too often will wear that flash and can render router inoperable.
There is a way to avoid this, but need to dig deep into the DD-WRT firmware. Moreover, for Broadcom-based routers there can be a simplier solution, but I only have an Atheros-based. If someone ready to run several commands to check it on Broadcom-based router, please PM. You can check which one you have at Status page of DD-WRT