This is not a stupid question. Yes we could engineer such a strain, the problem would be testing it given we would not be able to predict how dangerous it was.
Well if the regulatory agencies decided that they weren’t going to act then I suspect there would be a grass roots level spread of the strain anyway. This would be the worst way to use such a strain, but I don’t think it would be possible to stop this happening.
I don’t think we will get to that point. If we collect good data from the natural spread of any attenuated strain then I think the regulatory authorities will allow its use on the basis of this data.