5-4-4-4 systems (where 1S is 5 or longer, all other 1 level suit openings promise 4 or longer) are highly natural. However there is the problem where to park the exactly 4-3-3-3 hand type. One option is to open at the two level with all 18-19 balanced (e.g using BRASS or a Mexican 2D), and in first/second seat if 4-3-3-3 exactly to open 1NT if 14 and pass if 13. In third and fourth seat, the system becomes 5-4-4-3, allowing 3 card 1C openings on 10-14 balanced.

Here's an uber-natural snapshot design:

1C: 4+Cs, 10/11-21, balanced only if 11/12-14
1D: 4+Ds, 10/11-21, balanced only if 11/12-14
1H: 4+Hs, 10/11-21, 4Hs only if 11/12-14 and balanced without a four card minor (can be 4-4 majors)
1S: 5+Ss, 10/11-21
1NT: 14-17 balanced. 14s with a 5 card minor open 1NT, and 14 with 4-3-3-3 exactly opens 1NT in first or second seat.
2C: BRASS - usual 2C hand types or 18-19 balanced without a five card major
2NT: 20-21 balanced

In third or fourth seat, 1C: 3+Cs, 10-21, balanced only if 10-14 - 10-11s with 3Cs will open but not rebid.

Granted the 4-3-3-3 exactly and 14s will get too high sometimes by opening 1NT - however the system gains lots of 1C-3C bounces, where 3C shows four or longer Cs and less than a game invite. 4-3-3-3 exactly and 12-13 passes in 1st or 2nd seat, knowing there is a strong chance to be able to bid again, using a takeout double if the opponents open. Note that if you do open 1C with 4-3-3-3 and 12-13 (playing a standard type system), and LHO becomes declarer, your partner will often lead to your club "suit", so not opening 3 card minors has its advantages.

When balanced hands with just 4Hs are put into the 1H opening, it means that 1H-1NT can no longer include game invite hands, since the flat hand with 4Hs needs to pass 1NT even if 13-14.

Here's the core framework of a 1H response structure to handle this:

1S: 4 or longer spades

1NT: non-forcing, can be distributional

2C, 2D: Game invite with 6 or longer in the minor, or a game force 3 or longer in the minor. Opener rebids 2NT if 4Hs balanced. 3 of the minor over any of opener's rebids shows the game invite hand.

2S: artificial, 3+Hs, game invite, if just 3Hs then fewer than 4Ss

2NT: game invite, natural, 1 or 2 Hs, fewer than 4Ss, no six card or longer minor

With 5-5 minors, or if 5-4/4-5 in the minors and a bad doubleton in spades, either bid 1NT or make a game force in a minor - there is no invite for these hand types.