Considering that you can basically establish no invariants in the signals model, to me it sounds like a cooperative model is the way to go.
Have a way to poll for "outstanding" signals and deal with them accordingly, in some sort of queue (and the OS drops older messages or something, if they're important you'd deal with them).
The "freeze-the-world-and-do-this-thing-instead" model seems like the best way to introduce "my entire program is now broken"-style bugs. The OS deals with interrupts but the OS is also running by itself.
Have a way to poll for "outstanding" signals and deal with them accordingly, in some sort of queue (and the OS drops older messages or something, if they're important you'd deal with them).
The "freeze-the-world-and-do-this-thing-instead" model seems like the best way to introduce "my entire program is now broken"-style bugs. The OS deals with interrupts but the OS is also running by itself.