Sure you can,
After you've made sure you have no power in the work area, just open the access panel on you transfer switch, look at how much exposed wire you will need to make it a neat connection from your cord, remove the female plug and square up by trimming the wire ends if needed.
After disconnecting the locking plug box you now have, connect the wires of your cord directly in its place following the same wire color pattern.
Be sure to plan out your storage and note how the hard wired power cord will be secured in a way as to not have tension/pulling movement on it while in use.
Be sure to tighten the lugs properly where you make your connections, over looking that point will ruin all your hard work in time.
Now you can put that plug in box up for sale.
Dan & Loretta, US Army Retired Aero Scout Pilot
2012 Fleetwood Providence 42P Class A/DP
Spartan Chassis, 8.9L Cummins 450HP