Oups! i didnt see your second image when i made that first response, i was on an ipad. Yep it's pretty easy to replace a low res tile texture for a higher one.
Just open the dds texture from your vehicle folder with photoshop, resize the texture X2 or X4 , paste in your new texture and save back as dds. If you have outerra open with that vehicle spawned, you will see the texture update live.