Check with a tuner and make sure the 05 will not throw a code with the fans unhooked. You may have to get them to turn the pins off with a tune. Generally speaking, the electrical systems in modern vehicles uses a feedback algorithm to make sure a certain part is present or working... it does this by sensing the resistance in the circuit (in ohms). Even if a part isn't being called to work, the PCM will look for this resistance. If it's not there or it's drastically different than the parameters set for it, it'll trip a code.
Take the autoride (air suspension) system in the Denalis... if you simply unhook the air shocks or replace them with a non-compliant aftermarket shock, it will trip a code and show a Service Autoride message. To get around it, some companies (Arnott) will supply a resistor with the new non-autoride shocks to fool the system and make it think the factory shocks are still there and operating normally.
The next owner may be pissed to find out their "2005" doesn't have the electric fans.