The only problem with that is that we'd have to request every clan to re-submit their banners in a different format to ensure quality.
True, but maybe I could support you by creating a banner Pack separately, where only high-resolution banners are taken. And for Clans that do not provide a high-res banner, we could still insert them by scaling&sharpening. We would then have 2 banners packs, one normal and one with high quality. It is of course only a suggestion on my part.
I have another question ...
Which plugin do you use to store the DDS files? nvidia DDS for Photoshop?
The banner of Kapikulu (The Turks) in std_banners_g.dds, looks for example very blurry.