I like the concept of unrelated modifications remaining under warranty. That seems reasonable and also, crucially, amenable to the usual "Would a reasonable person say that damage X increases the chances of damage Y occurring?" type of test.
I don't like the "intended for general purpose computing" concept so much. For one, it seems to offer lots of easy wiggle room to manufacturers: Just say that your product is not intended for that, but for something marginally more specific. For another, it's not clear to me why general purpose computing ought to enjoy consumer protections that other manufactured devices do not. (One exception I'd grant is for safety reasons: If tinkering with a device could make it cause injury, fine, that device can be in a different class.)
I don't like the "intended for general purpose computing" concept so much. For one, it seems to offer lots of easy wiggle room to manufacturers: Just say that your product is not intended for that, but for something marginally more specific. For another, it's not clear to me why general purpose computing ought to enjoy consumer protections that other manufactured devices do not. (One exception I'd grant is for safety reasons: If tinkering with a device could make it cause injury, fine, that device can be in a different class.)