Don't think it will matter. A) the switches would get hot and melt if they were a restriction to current flow, and B) if you've had one apart, you'll see that the contact area in the switch is at least as large as you'd get connecting two of the power wires that feed it together.
The problem is usually in the regulator, the rollers, the motors, or the tracks. I'm not old enough to have had one of these trucks new to compare, but I suspect that all GM vehicles of that era had window motors that were underpowered when new, and only get worse as they get older.