Have guys guys tried to roll your own? I'm roughly playing an automated backup of one router to another one and then use a VRRP directly connected interface to detect and takeover/giveup all the interfaces (except for the directly connected VRRP one). It roughly seems to work OK, I lose some private keys (like ssh) and I haven't sorted out how to determine when to 'send' the backup but I am roughly able to switch between master/slave. The only downside is that it isn't pushing binary changes or anything, it reboots the second router to get it to takeover.
Curious if anyone has tried to pursue this and have any insight into the idea.
PS: I have an on startup script correcting mac addresses and switching to the proper A/B information. You might have noticed this as a glaring problem