I've also been dealing with the same issues when WIFI is not constant. I haven't yet found the best solution but interested in sharing the knowledge, hopefully together a viable solution could be reached.
Thus far we only have a small number of field devices we have deployed, we utilize a Project. In the event User1 made a change and User2 did as well offline, the race is on to which syncs back first, the other always gets a conflict and has to make a choice how to proceed.
I don't like this approach, but so far it is infrequent as the Users are typically assigned a system and there is little to no overlap.
Sessions don't seem to be the solution as our work packages are often 100's of pages/files and we might have 50 different work packages in the field at a time. 50+ different Sessions even with 1 merged file would be very cumbersome. All of these in a Session as individual files could also have problems. Within a Project we utilize a Master document that will link to individual files/drawings, this approach is not possible in Session (I haven't been able to get it to work) and we would need to adjust our whole front end work when making packaged.
I'm still not convinced I can't get a Session to work, and maybe utilize a Dashboard to drive to the correct Session. This is still a significant amount of upfront work compared to just using a Project for us at this point, and would require us to adjust how we already generate a Master document to link to files.