In my experience v1.46 resampled my 512x512 and 1024x1024 textures down to 256x256 and they looked horrible.
A single 256x256 texture image is definitely not enough to have a proper amount of detail on my weapons. 512x512 is perfect for the basic weapon, and maybe another extra image for attachments.
The trouble with using small textures is that the noise and dithering from the RGB-5:6:5 conversion is very noticeable. The larger you scale your textures, the dithering becomes less noticeable.
I pack my texture images as much as possible, and spend a lot of time UV mapping. However, I'm not willing to decrease a 512x512 image to 256x256. The loss of detail is shameful. Instead, to get around the v1.46 image size restriction, I break that 512x512 into four 256x256 image. It retains the same overall number of pixels.
For performance, this is actually worse. It means you have to load 4 files instead of 1 file. Each time you access a texture takes a certain amount of time - it may be miniscule, but if you extend it over a weapon addon with 20-30 weapon (120 texture images instead of 30) that can probably cause a noticeable waiting time while the addons load.
It's also more difficult to pack the unwrap shapes into smaller squares, you waste more border space.
I'm still undecided about how I will make the addon. I want v1.46 compatiblity, but it's going to mean more work, more files, more trouble. If I don't hear from enough v.146 users in this thread, I'll probably scrap the idea - so speak out if you care.