Since AoP 2.0.0+ should be unstable for some time and its scope has considerably changed, people including me may wish to stay in 1.9.1 for the time being. However, Lignumis 1.8.0+ cannot be loaded with AoP 1.9.1 due to the circular dependency. Is it possible to implement a support without marking it as dependent?

If I did that, load order would be wrong and more things break. Is downgrading Lignumis an option?

1.7.4 works fine though; if there's no new features upcoming, this will do for now I guess.