There will always be the possibility that the attenuated strain varies is some major but subtle way from the non-attenuated strains, but this is not something ever seen before with other viruses. If you demand to know everything and the answers to all possible risks up front medical science doesn’t advance.
I think your ideas are possible, but the likelihood of success is quite low and the effort required to do the proper studies is far greater than you estimate. Our resources are better spent on much more developed programs with better defined odds of success.
My helpful closing suggestion is to speak with some epidemiologists and clinical researchers to see if you can get some budgetary efforts for what you propose, or failing that, try to locate a review article or two. Good luck.
With the economic cost to the USA alone running at $500 billion a month are we really constrained by resources?
I have spoken to many scientists and clinicians about this. There is a great deal of activity going on to put this into action.
https://github.com/kordless/covid19_viz/blob/master/README.m...