(3) and (4) are easy in the sense that they are "normal" Leb sequences. 2NT is Leb and 3NT is "fast", and therefore lacking a Heart Stop and presumably with good long Diamonds.
It's (1) and (2), particularly (1), that are a bit more interesting to me. I know what I've written on the MOTOR sections, but...
I wonder if there really is much point in either of them being natural in any way at green vs red, especially (2), because Responder would have a fairly obvious Redouble over 1
- (X) - ??. I can't see much sense in (1) being Leb either, because MOTOR already gives us so many different ways of expressing different hand-types. Even if Responder has a Spade shortage here, a Redouble seems very attractive once Responder is 11-12 (let alone 13+) and if the Spade split is bad, the opposing Spade length will be
underneath Opener, which is probably good for us.
At red vs green, natural and invitational, or natural and GF makes perfect sense but I do now wonder whether it's worth reconsidering their meaning at favourable vulnerability.
I'd be interested to hear other people's view on this.