If you have a component fail you replace the offending piece, just as you would if a component failed. The fuses, relay and switches are just as easily replaced as anything you would use or replace if there was a failure. If you want to add circuits hopefully you are smart enough to take that into consideration when purchasing it and having a couple spare circuits. It is no different in functionality from any other relay panel and switch box out there, or from anything that anyone makes themselves, I've done that as well. The exception being systems like Racepaks smartwire and similar which is sealed. To each his own but there is nothing in a speedwire kit that is not easily fixed at the track with commonly available pieces from a good parts store, except maybe the serial cable which Best Buy would have.

If you run a delay box and it fails what do you do? If your electric water pump fails what do you do? Parts fail on all cars if you are serious racer who travels you will carry spares for common components that seem failure prone and not repairable at the track. Your argument against speedwire stuff only holds water for those who run things like Racepak Smartwire and similar systems. They are closed/sealed systems and non repairable, so if you choose to run those systems you have to carry a spare, albeit $2000 spare. If you pop a relay in a smartwire system you have to wait and hope it resets, otherwise you are dead in the water as you cannot bypass it easily or replace/reset that circuit. I have seen three of those boxes fail this year at the track. One team carried a spare the other two had to next day air one in.