Based on the thread on this ticket, T119412, it looks like we have addressed all of the concerns raised and can move forward with scrapping mobile's special:userprofile (T85929) page in favor of:
a header that includes a link to the users contributions, and
if userpage exists: show userpage as is
if user page doesn't exist: prompts user to create their own (if it is them) or notifies them of the absence (if it is another user)
If we don't hear any concerns by Friday 6pm GMT, I will ask that the web team scope the work to see if it can be included in our next sprint.