This is a product of trying dodge things, but it works perfectly well.
For mod user:
It is nothing fancy, just replace the leather short to mini-skirt and short boots to long boots.
In the "Material" folder of this mod there are 4 files for optional undies: "MPR_Muscle_Character_LEICOS106_d01.ktid.black","MPR_Muscle_Character_LEICOS106_d01.ktid.pink","MPR_Muscle_Character_LEICOS106_d01.ktid.purple",and "MPR_Muscle_Character_LEICOS106_d01.ktid.white".
Delete the default pink panty "MPR_Muscle_Character_LEICOS106_d01.ktid" and rename the one you prefer to "MPR_Muscle_Character_LEICOS106_d01.ktid" to use it.
For modder: Mod user can ignore the following nonsense.
This mod is testing two things:
1. adding texture material to slot. the LEI_COS_100 slot has just one clothe material and one body material. This mod add an extra material for the undies by adding entries to the "LEI_COS_100.mtl" and "LEI_COS_100.ktid". And it works! The limitation is all file names used must be already exist in the game. But that is not a problem for us -- bad boys, because there are lots of useless "body_z" file sets in the game.
2. another exciting trying of the mod is to transplant softbody grids between files! This g1m file is LEI_COS_106.g1m, but softbody grid 0 and 1 have been replaced with the ones from LEI_COS_100.g1m. Unfortunately, the process need to hex-edit the 0.soft file since g1m_xml.exe doesn't decode the softbody section. More detail would be post on the g1m tools topic:
This is a REDELBE layer 2 mod --- unzip inside folder "layer2".
Vagonumero13: rdbtool, g1mtools, g1m_xml, g1t_tools and REDELBE
Ausgeek: 3dmigoto tools for blender