I’m not an expert on either codebase but I believe the main driver of complexity with developing a browser engine is the sheer number of standards and how fast they change and multiply. Wikipedia has to update articles and maintain the server backend, which is no small task with such a global and comprehensive website, but Firefox has to do similar things on top of vastly more complex code with much more churn. There’s a reason Mozilla developed Rust as well.
If your wondering isn’t critical to the thought I would simplify to “the monkey who might be able to see my ears” or “can possibly see my ears”. Otherwise AbouBenAdhem has the best option, though I might also suggest “The monkey whose ability to see my ears I’m wondering about”; splitting the prepositional phrase is more strictly proper but I think it reads a little better like this.