For the first option: I would think you could make the implicit conversion an untyped macro itself, no?
For the second option: You can call a macro with multiple parameter lists, yes. Multiple lists at the call site will translate to multiple lists at the definition site, e.g.:
def myMacro(a: _)(b: _) = macro myMacro_impl
def myMacro_impl(c: Context)(a: c.Tree)(b: c.Tree): c.Tree = { ... }
Would be called as:
myMacro(...)(...)