1) If your motivation is heavy mathematical programming then I hear you, but beware that you are the minority of the language's userbase, (more generally, most application-level programming languages' userbase), it's not something most people care about.

If you want to write clever DSLs and/or name methods in ways that save keystrokes like in scala, NO, please.

2) There are libraries such as runtypes and io-ts that integrate well with the static type system