Custom HTTP Monitor help

Well, have you think an external monitor a good idea, see this article from Deb Allen. You can use arguments and define variables to pass to the script run. I would do an bash script external monitor passing at minimum, as argument the [IP :: local_addr] that will contain each destination IP. I think that's it solves for you.

https://devcentral.f5.com/articles/ltm-external-monitors-the-basics