Here's the system I'm designing for mid-chart (ACBL convention chart) pairs:

Note: N12 = Not vulnerable in 1st/2nd, V34 = Vulnerable or 3rd/4th

1C: Big, 18+ or 15-17 with playing value, either:
1) 15-17 unbalanced, a 6+ suit or a 5-4-3-1 or a 5-5
2) 18+ any

1D: Mini catch-all, 10-14, promises 4 card major or 5Hs except if 13-14 balanced N12.
Either:
1) Balanced, or semi-balanced:
1a) a 4 card major, 11-14, 11-12 optional V34, 11 optional N12
1b) 5Hs, a 5-3-3-2, 2-5-4-2, 2-5-2-4, 11-14, 11-12 optional V34
1c) N12 only, 13-14 and no 4 card major
2) 5Hs, 10-14, not including 1b:
2a) 4Ss, 5Hs, 10-14
2b) 3Ss, 5Hs, singleton in a minor, 10-14 - optional, can open 2H instead
3) 4Ss, longer minor, 10-14
4) 4Hs, 3Ss, 5 card minor, 10-14 - optional, can open 2m instead
5) Any 4-4-4-1 10-14 (the 1-4-4-4 hand is the only hand where a singleton S is possible)

1H: 15-17, balanced or semi-balanced. Can have a five card major or six card minor. Can be any 4-4-4-1. Not a 5-4-3-1 unless singleton is A, K, or Q.

1S: 9-14, 5+Ss

1NT: 11-14 V34, 10-12 N12. 4 card major or 5Hs possible only if minimum (11-12 V34, 10 to bad 11 N12)The objective here of no four card or longer major if maximum is that responder does not have to move out of 1NT on bad invite hands that have a four card major.

2C: 5+Cs, 10-14, fewer than 4Ss, if just 5Cs must have a singleton. 3-4-1-5 can also be opened 1D.

2D: 5+Ds, 10-14, fewer than 4Ss, if just 5Ds must have a singleton. 3-4-5-1 can also be opened 1D.

2H: 5+Hs, 10-14, if just 5Hs must have a singleton and fewer than 4Ss. 3-5-4-1 and 3-5-1-4 can also be opened 1D.

2S: 5-9, 5+Ss

2NT: 6-5/5-6+ in majors, 10-14

Since almost all 10 counts are opened N12, for not vulerable 34 (N34), 1NT should be 12-15 (a major only if 12-13 and optional), and the balanced range in 1D should be 12-15. 1H will be 15/16-17 balanced, 15s with a five card suit.

1NT in N12 should include the dismal 13s - the 3-3-3-4 and 3-3-4-3 hands.