First, this is ambiguous:
_contract = new MyContract();
Currently this is valid code if _contract has already been declared because = can be used in in expressions.
Also, I think that it reduces readability. Now you cannot be sure whether it’s a declaration of a new variable or an assignment without knowing the context.
I think it’s less error-prone when declarations have a dedicated syntax. For the compiler to distinguish them, we’d need for example a keyword that introduces a declaration:
var _contract = new MyContract();
which, incidentally, used to be a feature of the compiler but was removed long ago. Do we want var back? 
Second, I really liked the idea of inline structs, which would already allow initializing them in a DRY way:
MyStruct memory B = {bar: "baz"};
Do we really want to have yet another way to do this? Solidity has a lot of influences from C++ but having a million ways to initialize stuff fortunately wasn’t one of them so far 