Hey list,
just for the record, during the past weeks we've been discussing how to improve hidden services hosted on mobile phones in this here trac ticket: https://trac.torproject.org/projects/tor/ticket/16387 Discussion has also spilled over ticket #18620.
The discussion also has a design aspect as some suggested improvements would require protocol changes, hence I'm informing this list in case some people are interested in jumping in and participating.
For example, for some use cases it might make sense to have an HS -> IP cell INTRODUCE2_ACK that acknowledges the receipt of INTRODUCE2 cells, so that the IP knows that the intro circuit is active and the HS received the introduction request before sending out its own INTRODUCE_ACK to the client. That's because mobile hidden services are unstable and their intro circuits break frequently, causing reachability issues. See the second part of https://trac.torproject.org/projects/tor/ticket/16387#comment:8 for more background.
Have a good day :)