If you like the look of the new units but would rather they change how the existing units look rather than adding new ones then read on and I'll give you a quick guide on how to change the mod to suit your needs:

First get PFM or another program that lets you edit the games .pack files. Find the mod (c2_empire2_public.pack) and open it with your program of choice.

It should be in one of the folders here: Program Files (x86)\Steam\steamapps\workshop\content\

The 'skins' are called variant mesh definitions and if you're using PFM you can see them at the bottom of the mod tables.

Most of the mods tables should be deleted entirely except for:

'unit_variants_tables' & 'variants_tables'

These two tables assign a unit its in-game appearance.

What you want to do now is open the data.pack file in the main TW2 install location and find the same two tables there. Find the entries for the various empire units e.g. 'wh_main_emp_inf_halberdiers' and copy the entire line for each unit - then paste it back into the mod which will completely overwrite the changes that that mod makes.

You now have a mod that has new unit variant meshes and the tables that govern which variant mesh a unit uses - now you need to link them together.

Open the 'variants_tables' and look at the column named 'variant filename'. Change each entry to the name of the modded variant mesh.

e.g. change the empire halberdiers from 'emp_state_troops_halberdiers' (the vanilla mesh) to 'T3_halberdiers' (the name of the modded mesh).

Open the 'unit_variants_tables' and do the same for the 'variant' column changing the old vanilla entries to the new 'T3' versions in the mod.

Save the mod and that should be it - DISCLAIMER - I'm writing this off the top of my head with PFM open for reference, if you try this and it isn't working then please reply to this discussion and I'll troubleshoot the problem with you.

Have fun!