Installing an outlet to charge while closed

Hello All, This is my first post, I have found a ton of great information here, I bout an '03 2720SL about 3 weeks ago and am just trying to get everything figured out prior to camping season. I would like to charge it up and pre-cool the fridge while closed up in the garage, to avoid pulling it out into my driveway on Thursday evening to start for a friday trip. I have read a ton of threads about how to best charge the TM while closed and saw that several people just drilled a hole and pulled the main power cord into the back bumper storage so it is accessible while closed. I am still considering this but have come up with another potential solution. I bought an outlet that has a Male end on it so you can just plug the female end of an extension cord directly into the outlet, it is sealed and spring loaded. I am thinking of drilling a hole through and putting this on the bottom of the TM somewhere near in the battery box. I will then run a 12 ga wire up to wherever the regular plug is connected to the vehicle and wire it in at the same place. I would never plug both in at the same time. Would this work? Anything I'm missing or overlooking? Thanks in advance for your input.
Pat