Removing IAP and other extensions is definitely on our radar, we just have to schedule these things in a good way. It’s in our roadmap (See the category “Modularization”).
Apart from the IAP stuff, remaining use of the PlayServices, I believe it’s used for sys.get_sys_info() (ad_ident and ad_tracking_enabled), and if we can perhaps detect that we don’t have that specific manifest key, we can skip invoking that part as well. I’ve created ticket DEF-3493 for this.
We have no ETA for these particular tasks though.