Precision

1	16+ HCP, 15 HCP possible with a distributional hand
1	11 - 15 HCP, 4+
1	11 - 15 HCP, 5+
1	11 - 15 HCP, 5+
1NT	12 - 15 balanced
2	Precision 2: 11 - 15 HCP, good 5 + 4/ or 6+
2	Mini-Roman: 11 - 15 HCP, 3-suited with short : 4414 or 4405
2	Weak Two in
2	Weak Two in
2NT	22 - 23 balanced

Precision as it was originally intended is too meek for me. One can make Precision more agressive and free the 2 bid. Notice that the 1 bid is natural unless it is a maximum. I think the inclusion of the singleton diamond hands into the 1NT opening bid is a small sacrifice. The opening bid structure could for example look like this:

1	16+ HCP (rule of 25)
1	9 - 15 HCP, 4+ or 14 - 16 balanced*
1	9 - 15 HCP, 5+
1	9 - 15 HCP, 5+
1NT	11 - 13 balanced*
2	Precision 2: 11 - 15 HCP, good 5 + 4/ or 6+
2	Ekren: 6 - 10 HCP, 4+ 4+ or 22 - 23 balanced
2	Weak Two in (3 - 7 HCP)
2	Weak Two in (3 - 7 HCP)
2NT	Unusual: Weak / Strong with 5+ 5+

^* Includes hands with 4 4 1 4

Responses to 1

1: 0 - 7(8) or 8⁺ with 4441 (Impossible Negative)

1: 8⁺, 5⁺

1: 8⁺, 5⁺

2: 8⁺, 5⁺

2: 8⁺, 5⁺

2: 8⁺, 5⁺ 4⁺ minors

2: 5 - 8 HCP, 5⁺ + 5⁺ second suit

3: 5 - 8 HCP, 5⁺ + 5⁺

3: 5 - 8 HCP, 5⁺ + 5⁺

3: 5 - 8 HCP, 5⁺ + 5⁺

3: AKQxxxx in a suit