No, I don't think your suggestion can be rubbish as that can have of some value too. Maybe this can be taken up by some people who are very much involved with bitcoin and its processes. Indeed, if the same hashing power can also be used with other worthwhile cause then bitcoin as an ecosystem can be more valuable and can be serving humanity more most especially that it is taking a chunk of electricity to run the whole thing. I am hoping that somebody can propose this or if the idea had already brought out sometime then maybe it can be re-examine to see if integration can be possible. Now, am not really an expert on bitcoin but I do agree with what you mean.