Hey mate, Idont want to be rude, but it seem like you absolutely dont understand the problem. Im using 4096x4096, I cant go higher, I can split my mesh to smaller pieces, but that basicaly means I have to remodel it.BTW Green means IDEAL texel density. Blue means LOW texel density. My friend Im not idiot, and I know that pink color just means that one specific mesh is selected.
If Im still wrong I apologize, but my problem isnt low texel density, my problem is, that my shadow map is not matching texel density. read this: View Modes | Unreal Engine Documentation