If your needs are complex, you have better chance by mixing different options in the completely declarative syntax of systemd than mixing shell snippets from different scripts using different styles.
In any case systemd happily launches LSB-compatible init scripts, you literally don't lose anything.
> In any case syst emd happily launches LSB-compatible init scripts, you literally don't lose anything.
Yes, I do. I literally have piles of unwanted systemd on my system.
Arguably, reinventing multiple complex wheels is often a not particularly good choice.
So either you're implementing something really novel in your init script (which does not sound like the best place for it) or it's something that may benefit from a single, shared and tested implementation.
And, again, you can still fallback to LSB shell scripts if you really need something incredibly special: my point was that, bloat notwithstanding, you don't lose any feature but gain many.