Tweak extensions dependencies...?

I wonder if it’s possible to control extension dependencies… Consider this scenario that I’ve stumbled upon. Package A exists and has some deps. It’s one of those packages that both defines an interface and provides various implementations of it. Those implementation have dependencies for their work, namely things like HTTP 1. Now I’m writing package B. It’s mostly done, and I want to write an extension for A implementing the interface of B, lets call the extension ABExt. A doesn’t require HT...