What F5 is describing is leaving the stator grounded with lights on AC. Cheapo rectifier to get DC for specific devices which are not grounded. I've never used a capacitor instead of a battery, but it will work. You are asking about isolating the stator and not having a battery. This should be OK.
Keep in mind that battery charging needs extra voltage. This is done with the white wire. Bottom end of the stock stator is grounded. All the lighting windings are in series. The yellow wire taps off most of the way up the windings. The white wire is at the top of the windings for maximum voltage output. Without a battery you do not need the white wire. Leave it totally unconnected. Hook your rectifier input to the yellow wire and the bottom of the windings which have been lifted (unsoldered) from ground. Solder a new wire to this lifted ground (any color is fine, yellow would be good). Make sure the new connection point is protected with heatshrink. This takes care of the rectifier input.
Now the rectifier output (black?) connects to the frame as your new DC ground. The other rectifier output wire (red?) which is DC positive goes to a fuse and then to your devices (lights, etc.).