[Kungsgeten]

This is an idea over a Swedish Club (weak NT or 17+ any). We currently play 1♣-1M; 2♦ as Odwrotka (GF, 17+ with 3+ major support), and use the 1♣-1M; 2♣ as natural (GF, 17+ with 5+♣). We earlier played the 2♣ rebid as an unbalanced two-suiter with at least one minor, which was a reasonable alternative I guess.

Ulf Nilsson (ulven on BBO) have a system using unbalanced 1M openings, and when responding to these he use 1M-2♣ as GF with 2+M, and 1M-2♦ as GF with short M and not 5+ cards in the other major. This inspired me to think about a similar structure in our 1♣-1M sequence. Our 1M response can contain:

1. A balanced hand with 4+ major and 8+ hcp.
2. An unbalanced hand with 5+ major and 8+ hcp.
3. An unbalanced hand with 4 card major and 5+ minor, and 8-11 hcp.

This is a lot more nebulous than Ulf's major suit openings, but I've tried anyway. The idea isn't to have full shape relays, but to give information or ask for information depending on the hand type in order to find a fit. Here's after 1♣-1♥:

1♣-1♥;
1♠ = 4♠ with weak NT, or 5+♠ and 0-2♥ with 17+.
1NT = Weak NT, no major.
2♣ = Most hands with 2+♥ (3+ if 5+♠), 17+.
2♦ = 0-1♥ and 0-4♠, 17+.
2♥ = Weak NT with support.
2♠ = Natural GF, good spade suit and short hearts.
2NT = Not quite sure. We currently play it as "natural" 20+ (we open 1NT with 15-17 and 2♦ with 18-19) with 1 or 2♥
3♣♦ = 6+ suit, extras (20+), 0-2♥ and unbalanced
Higher = Not sure...

The most interesting part is probably the 2♣ and 2♦ rebids, so lets check them out. The idea is that these are symmetrical over a spade opening too.

1♣-1♥; 2♣---
2♦ = (Semi)balanced, 8+. Could be 2-4-2-5 or 2-4-5-2.
2♥ = 12+ unbal with 5+♥. 2♠ relays.
2♠ = 8-11 with 4♥ and 5+ minor. Not 5422.
2NT = 5♥ and a four card side suit, 8-11.
3♣♦ = 5-5, 8-11.
3♥ = 5-5 majors, 8-11.
3♠ = 6+♥ and a singleton (3NT asks), 8-11.
3NT = 6322 or 7222, 8-11.
4♣♦♥ = 6+♥ and void, 8-11 (4♥ is spade void).

Some more details:

1♣-1♥; 2♣-2♦ (balanced);
2♥ = Relay.
...2♠ = 4♥, 8-11. 2NT asks for other four card suit.
...2NT = 4♥, 12+.
...3♣ = 5332, 8-11.
...3♦ = 5332, 12+.
...3♥ = 2-4-2-5, 8-11.
...3♠ = 2-4-5-2, 8-11.
2♠ = 5+♣ (2NT would be a relay)
2NT = Natural.
3♣ = 5+♦, 4♣.
3♦ = 5+♦, 4♠.
3♥ = 6+♦.
3♠ = 5-5 minors, better diamonds.
3NT = 6+♦, not forcing.

Not quite sure what breaking the relay should show in terms of strength and heart support, but probably doubleton heart and minimum strength?

1♣-1♥; 2♣-2NT (5-4 pattern);
3♣ = Asks shortness, sets major as trump suit.
3♦ = Asks side suit.
3♥ = Clubs, heart doubleton.
3♠ = Diamonds, heart doubleton.
3NT = To play, heart doubleton.

This post is getting long, but there's also the 2♦ "rotka":

1♣-1♥; 2♦ (17+ with 0-1♥)---
2♥ = Waiting.
...2♠ = 5+♣. May relay with 2NT.
...2NT = Three-suiter.
...3♣ = 5+♦, 4♣.
...3♦ = 5+♦, 4♠.
...3♥ = 6+♦.
...3♠ = 5-5 minors, better diamonds.
...3NT = 6+♦, NF.
2♠ = 4(+)♠, unbalanced.
2NT = Good 6♥ or non-solid 7+♥.
3♣♦ = 5-5, extras or a weak major suit.
3♥ = 7+♥, (semi)solid vs singleton.