My friend and partner, Ken Eichenbaum and I have been working on a simplified version of part of the Super Standard System by Mats Nilsland.
We have incorporated most unbalanced hands into a 2D opening, including 4-4-4-1 hands. With those, you rebid 2♠, which either shows a 4-4-4-1 hand or a 6+ spade hand. The simple relay of 2NT allows Opener to show his stiff submarine-style (3♣=4414, 3D=4144, 3♥=4441) or rebid 3♠. This of course requires that hands with 5♠ and 4♣/4D/4♥ be opened 2♣.
That's fine with us. We also did not want to lose the two-way balanced hand approach from Kokish. What we did was to change the three-level response structure around:
3♣ shows 5+ clubs (0-4♥/0-3♠). 3D asks for more info as to the majors, with Opener bidding 3♥ with four hearts or 3♠ with 0-3 hearts but three spades. 3♥ by Responder shows 5♥ and maybe 5♠ (opener can introduce spades). 3♠ shows 5♠ but not 4♥. This handles all situations.
3D by Opener denies a 4-card major.
3♥ by Opener shows 4♥/5+D and 0-3 spades.
3♠ by Opener is minors, 5-5, with no 3-card major. With a 3-card major, Opener bids 3D. If Opener bids 3♥ and Opener has a fit, great. If not, he bids 3♠ before a possible 4♣. If Opener hears 3♠ and has a fit, great! If not, he might bid 4♥ with a big 0355.
3NT by Opener shows 1444, the missing pattern.
There is more, but you can work out what makes sense. The idea is to simplify (missing 5-5 nuances immediately, but easier), save the 2-way balanced hand handling, but retain ability to handle the main problem hands effectively.
We are supposed to try this out this weekend, if we feel ready.