I'm referring to your comment about a plug-in digital replacement for VHS tapes, not your comment about cameras. A plug-in VHS device would be subject to most of the same limitations as real VHS tapes, which is to say, the very best you could hope for is composite quality video, and in reality you'd get substantially less. The cost of such an interface, however, would be far more than the cost of just putting a composite (and/or HDMI) interface on the device to begin with. This sort of thing might make sense with cassette players in a car radio, where there are no other ways to connect to the radio, but that's not the case with a TV. Any solution you could come up with would cost more and provide lower quality than just plugging the new device directly into the TV.
In terms of the camera comments, the value is in the lenses, not the cheap semi-disposable camera bodies. You can simply buy a new digital camera body for your existing lenses. A modern APS-C DSLR will provide better image quality than 35mm film, albeit with a crop factor and reduced depth of field, and it can use your existing lenses. Possibly with adapters, depending on what type of lenses you have. They're $300-400.