Composing a repertoire for a group of readers requires to take the assumed average taste and needs as a benchmark. While an individual repertoire can be subjective to a certain degree, a generic one has to adhere to a stricter body of principles:
With White I am trying hard to deliver += and with Black the goal is equality. This is possible by carefully selecting what line you are going to analyse. It is a constant search for quality.
Many players commit the mistake to go for cheap solutions in order to safe time. This side line approach might take some opponents by surprise in the beginning, but in the long run it leads to dull (with White) or bad (with Black) positions, once the opponents start to prepare. Then, the player changes to the next cheap solution and so on. In the end, he will have spent more time on his openings than the quality guy, with the difference that he is basically left empty handed while the other one has forged a solid repertoire over time.
The lines I choose may not be too complicated and variation-heavy. Personally, I don’t like to rely on memorising lines, risking to fall into the abyss, if I take a wrong step to the left or right. I prefer lines which contain a high degree of order and are ruled by strategic principles. That way, I am able to find the right moves by logical deduction, when being out of the book.
Defending can be an efficient way to win a game of chess. Many strong players like to trade structure for activity. “Deep Sicilians” such as Scheveningen, Najdorf, Kan, Taimanov and others are good examples. That said, playing with activity is easier than playing against it. Hence, in the majority of the cases I choose active lines.
In almost no case I expose my readers to systematic attacks, as defending the king is an extreme form of defence, while even defence in its milder form is not very popular. There is also a pragmatic side to it. The weight of each mistake is much bigger on the defensive side. Each mistake as a defender can be your last.
5. Positional Depth
The same way I dislike wild positions I shy away from boring structures with only very few winning potential. Also with Black you should be able to extract the full point from your lines, as you might face inferior opposition. This goal of retaining your winning potential can be achieved by the creation of imbalances. Personally, I take care that all my Black openings have at least some kind of imbalance, where I can base a winning plan upon.
If you have ambition, time and energy, by all means entertain a (partially) flexible repertoire, with options for sharp and solid play, depending on the situation. That way, you also widen your horizon.
The majority of readers, however, are amateurs with a need for economical solutions. Hence, my general view is that your lines should be versatile, which means solid and rich at the same time – fit for all occasions.
In a perfect world we can combine quality with originality. While this is difficult to achieve for the amateur, many strong professionals are constantly searching for solid under-the-radar-lines, in order to find their opponents unprepared.