There is also a way to change your wife's equipment in-game. Open conversation.txt in the module folder and search for this line:
dlga_spouse_talk:spouse_household_possessions 69631 564 0 Let_us_take_inventory_of_our_household_possessions 723 1 2041 1 360287970189640508 NO_VOICEOVER
Underneath, paste in this line:
dlga_spouse_talk:spouse_inverntory_wife 69631 564 0 Let_me_see_your_equipment 0 1 2051 0 NO_VOICEOVER
So it looks like this:
dlga_spouse_talk:spouse_household_possessions
69631 564 0 Let_us_take_inventory_of_our_household_possessions 723 1 2041 1 360287970189640508 NO_VOICEOVER
dlga_spouse_talk:spouse_inverntory_wife
69631 564 0 Let_me_see_your_equipment 0 1 2051 0 NO_VOICEOVER
dlga_spouse_household_possessions:spouse_pretalk 4095 842 0 Anyway,_that_is_the_content_of_our_larder. 840 0 NO_VOICEOVER
The numbers in red will need to be the same, otherwise it won't work. Copy them from the "household possessions" line into the new one. They will probably be different in your game. And yeah, inventory is spelt wrong lol. But that's how it is, and it works.
Then you can change your wife's clothing as often as you like without having to edit the NPC continuously. Enjoy!