I cannot really remember since i have not played the Pit for quite a while, at least 1,5-2 years ago. But, i thought mod companions follow you into the Pit, the vanilla ones have to stay behind before you can start it!? Just give all your gear to them, pretend you are the distraction while they sneak into the Pit. Mod companions usually have some sort of device so you can call them to your location if you loose them. Just be a little creative in thinking where you hid that calling device before you started the distraction ;-) For immersion sake you could make a small mod that adds the companion calling device only after you visited a restroom :-) ;-)
Or you could just make sure you have the itemcode if it is taken from your inventory upon entering the Pit and use the console to add it to your inventory.
What you do after that is up to you, dress your companion in slave clothes also and play through the Pit, but with your better weapons, or gear up and go on a killing spree.
I'm about to finish FO3 main quest and head for Vegas to pick up Willow & some other mod companions. I'll take them to the Pitt sometime next week to see what happens :-)
I think that would solve your problem with the least effort and no complications for the rest of the the Pit DLC apart from immersion.