Splash page to users when F5 load balancers are down?

Hey guys! So I have an interesting question for ya'll. We have several applications sitting behind Load balancers. The problem with that is that when the load balancers become unavailable...obviously, the application does too because it relies on routing traffic via load balancers and is configured as such. So when they are down and a user goes to the application routed to those load balancers...they get a generic unavailable page. Not very user friendly and it creates a lot of confusion. What I'm trying to figure out is a way to generate a splash page that is available to the user who tries to browse the application when the load balancers are down. So instead of getting some not very useful error they get a page saying that the load balancers are down for maintenance. Originally, I thought maybe an iRule but then HA remembered that if the F5s are down they can't do iRules...or well...anything. Surely, I'm not the only one out there who has thought about this? Thoughts?