I think you're getting at just the mods who are under a few megabytes.
If they can find a way to add them, that would be great, but I'm not holding my breath.
No, I'm not... injectors or texture packs effect FPS very much, which is what you stated. Same if you had a mod that spawned 1000 cabbages rolling down a hill, to much at one time will effect the FPS. Most mods however, do not do this... size is irrelevant. They would be concerned about these few mods that would push the system to far. However, BS has already stated and verified that on a dev console mods on the 360 and PS3 work just fine.
Pretty much, almost every mod in the steam workshop could be added to a console with little issue.