I totally agree with replacing existing ERB helpers content to mount react components. The example @ezr-ondrej mentioned is a new component though, there’s no helper for datetime as of now. The select is I believe the new implementation, not the select2 we use. I agree that having these helpers is beneficial for time being. If we prefix them with react_, we know that we should only use them on places where we combine ERB and react. So 
for the proposal from me.
Once we feel there’s minimum of ERB and all plugin maintainers write UI in react, I’d change my mind. Given State of React for Plugins I don’t think that happens anytime soon.