Samsung did this: https://www.dpreview.com/reviews/samsung-nx1 but gave up the market in 2015.

That was likely a good idea from a cost-benefit perspective, as standalone cameras continue to decline in unit volumes: https://www.dpreview.com/news/7719403699/cipa-s-november-num..., but it's a shame from a technological progress perspective. You are totally correct that a camera body really ought to be an Android device, but camera makers have not done that—which likely contributes to their fall in unit sales.