I don’t know if the engine already performs something like this, but I would suggest the landscape tool analyze the weights and then auto mip down textures that are lower opacity in the blend. If you have two 4k textures, one at 30% and one at 70%, you can pretty much go all the way down to 1024 on the 30% one because it will barely have a noticeable visual difference.
Here is a quick example of what I mean. I tried to paired up a couple of REALLY contrasting 4k textures where I have a dark base texture and a light, high frequency, texture blending on top; at 50% opacity. Oh and excuse the slight offset, I must have nudged it on accident:
Here are what the base textures look like (only uploading the 1k versions to show what I mean)