Well... about the PSU in you're case it might be OK, I would still not do it but ok... I've seen far more dangerous looking AT PSU switches so other's might not be so lucky with the switch.
As for the converter cable I'm sure it'll work but the extremely long power cable together with a "funky" connection in the middle will most definitly have worse power output compared to a shorter power cable without the extra connectors in the middle.