It takes as much time as creating and rigging a model of panties or ANY model. It should be scripted a little for 3dxchats "enviroment". Or having 2 models of panties: classic look and deformed (pulled) that players have to wear/unwear by clicking on icons.
Reminder. Every clothing has about 3 object in one. High poly, mid poly and low poly. Usual optimization that not every indie game has. But 3dxchat has that. Fortunately. Good optimization for an indie game.