If you're getting a slideshow on that kind of hardware then your problem is elsewhere. I've run it on an NV GT230M and an AMD 6490M and both run it just fine - the NV is slightly faster but the AMD has better image quality and more consistent/stable framerates.
The partially resident texture option is new to the 7000 series, and did not exist when the engine was originally built. It would require a patch which may in-turn require some heavy reworking of the engine code. You can't just click on a button marked "use partially resident textures" here.
GPU Transcode is an NV-only option for now because it uses CUDA. It couldn't use OpenCL at the time because OpenCL was not mature enough; I'd expect to see it moving to OpenCL for either a future patch or for Doom 4, which would enable GPU Transcode on both NV and AMD.
Neither of these are relevant to your problem because you should not be getting slide-show performance with that hardware. There are plenty of people with lower-specced AMD hardware who get smooth and stable performance from it, so like I said you need to look elsewhere for the cause of your problem.