Knoppix has (in the kernel configuration) support for your IO-APIC (instead of the older XT-PIC) interrupt controller.
Using APICs allows IRQ numbers higher than 15 (possibly only up to 31, but I don't know for sure).
If you can manage to get SuSE to enable APIC support, that might be a good workaround. If nothing else, it'll give you a bunch more IRQs to use. The option is somewhere (in the kernel configuration) under "processor type and features", IIRC.
I tried APIC support a while back, but my USB mouse stopped working right -- it looked like the interrupts were just never getting transmitted to the driver. Probably just something with my board and/or the way I configured that kernel, though (I've got a KT333). If your USB devices work under Knoppix, that would be a start.
Edit: Just saw the second post. Yeah, modifying your bootloader to do that would probably work too. As long as you don't need ACPI for something else...