being nice to all kind of mangled formats/dimensions is useful during production, but once you hit the finish line, store the stuff in the exact format you need in memory.
We don't even allow that.
EVERY resource which is loaded, during every stage of development, is a processed one. All images are converted first to DDS then to our custom format (basically a smaller header with a platform specific payload attached which is in the hardware format required) so they can be directly streamed in as fast as possible.
The only difference to development vs final build is that for the final build the various packaged files are consolidated into larger volumes which are compressed using zlib.
There is no good reason to be dicking about at runtime with custom formats and if you aren't giving the GPU DXTn/BCn compressed data to work with then you are Doing It Wrong and a GOOD DXTn/BCn compresseor can take quite some time to run so if you are trying to run time compress to any decent degree then there is no way you'll get fast loading times.