For example, if I have ext-ev installed, Composer still suggest installing ext-libevent while it's unclear from a consumer's perspective how much value this provides.

Note that #113 has improved the suggest keyword description for each extension somewhat, but I believe this is more an issue with how Composer suggests these dependencies and now really something that can be addressed in this package.

As an alternative, I suggest simply dropping the suggest keyword completely. Is much gained by having this in place? Instead, I would suggest updating our install instructions to detail why having either extension can be a good thing (under what circumstances anyway?).