The basic idea is –
1♣ = 5-card spade suit, 12+ HCP, or 22+ HCP any distribution (equal a 2♣ opener in natural systems)
1♦ = 5-card club suit, 12+ HCP, or 20-21 HCP balanced (equal to a 2NT opener in natural systems)
1♥ = 5-card diamond suit, 12+ HCP, or 18-19 HCP balanced (equal to a Mexican 2♦ opener)
1♠ = 5-card heart suit, 12+ HCP, or 15-17 HCP balanced (equal to a 1NT opener in natural systems)
1NT = 12-14 HCP, balanced, denies a 5-card suit
The proposed first round responses are –
1. Cheapest available bid, including double and redouble, shows 8-12 HCP, may or may not have a 3-card fit (12 + 8 = 20, our side has at least half the HCP)
2. A bid of 1-under the suit shown asks opener to bid the suit shown, less than 8 HCP, may or may not have a 3-card fit
3. Any bid above the suit shown is natural and pre-emptive, denying a fit with opener
4. A bid of the suit shown is game forcing and asking opener to bid out his shape
Before bothering about the 2-level bids and higher, can this work?