I will soon start building my new Panda MATV MRAP, and was wondering if anyone could point me towards any gun upgrade for it, as well as any other upgrades worth buying for it.

You might go on to Blast Models for a couple of interesting additions to the MRAP but hurry, they are closing to reorganize/downsize
this is the link to their mine roller
http://www.phpshopxml.com/blamod.shop/CID/3aca2a9bb8360c4e0c3ecdb8dd15709d/function/itemPageDisplay/shopItemCode/BL35188K

I was looking but no longer see the RWS specific for the M-ATV

I would sudjest looking for replacement wheels.
The tires on the kit that I have were packed inside the engine hood, and started eating into the plastic.Lucky it was the inside of the hood and not the outside.
I purchased replacement wheels from sprue brothers.
They are currently out of stock, but maby they will get them back in.
They are made by DEF Models
Hope this helps.
Donald

Have you try Pro Art Models? they have a few sets like interior, wheels & spare wheel + mounting rack, and radio set etc....

I just remembered.
If you are looking for some detail, check out
www.skpmodel.eu they have a set of headlight and tail light lenses with all the side reflectors included. They are made of photoetch stainless with clear and color resin for the lenses.The item number is #SKP156
Donald