If you wanted to see a way to do this, here goes. Pics at the bottom of the description.
Not recommended if small kids are likely to be around your car when it is unlocked and open. For other situations it can be a useful feature—shop work, heat/rain, garage naps, stakeouts.
The good news: since the entire window system is powered by one pink hot wire to the master (driver’s) switch, changing the power source is easy.
The bad news: not much working room behind the fuse block.
In the Fleetwood’s original design, the retained accessory power (RAP) circuit powers the windows when the car is on. It continues when you turn the key off, but only for a few minutes. And, the RAP circuit goes dead the instant you open any door. To get keyless windows, you must change the window power supply from the RAP circuit to a suitable always-hot source without affecting other circuits.
Bad option: Bypass the RAP relay and use a length of wire to splice the pink window power lead into the always-on orange power supply wire leading into the RAP relay. This is easier than dealing with the fuse box, but the only circuit protection will be Maxifuse #2, which serves lots of other circuits as well.
Better option: more under-dash work but taps into the fuse box and isolates the window circuit better. I used the 20-amp circuit for the trunk light and electronic level control (ELC) sensor. I don’t use ELC any more so the circuit is only the trunk light and now the windows. Access to the fused wire isn't too awkward (the fuse is fourth from the right on the bottom row). It has only one wire leading out from it, since the hot side is fed by a common feed wire that serves multiple fuses. That ELC wire is a slightly lighter gauge than the window feed, but the length is short and repeated testing of the windows didn’t heat up the wire at all.
IN A NUTSHELL
Remove the access panels and remove the ELC fuse.
Loosen the blue wire retainer on the back of the fuse block and use a pick from the fuse side to release the appropriate wire terminal (bottom row, fourth wire from left, orange) while pulling it from the rear.
Unwrap the big harness to get some slack and splice in a length of wire (I used some leftover 14-gauge tinned marine).
Reinstall the wire terminal in the fuse block and push the blue retainer back into place. Now it's test-light time—with no fuse, the end of your new wire should have no power. With the fuse in, you should have power with the car off.
Disconnect or clip the pink power wire to the window and splice in your new extension. With the key on, use a test light to ensure you connect to the window side of the pink wire (not hot), and not the hot side of the pink wire from the RAP relay. Do this near the door wiring conduit, NOT near the RAP relay, because the relay’s hot pink tees off to feed some other things. Now cap off the unneeded hot pink and you’re done. The windows work just the same as before, but with no key.
I know—with a couple of suitable terminal ends I could have done a cleaner job at each end of the jumper wire, running it right into the fuse block and into the harness connector.
It’s also possible to include an on-off switch in the jumper wire to disable the always-on, if so desired.