This is a huge problem for me, not because it bothers me, but because it bothers others who I collaborate with on meeting agendas and the like. They want to lock down our documents, or use static documents, to avoid this problem, which kills a huge value offered by Google Docs.
While we wait for a better answer that truly addresses your question (I think it had it's time), here are some workarounds that I would recommend to someone with this problem.
Use headings and the
Document Outline feature to click back to what you were working on
Outline feature has come a long way, and at this point it's invaluable.
If you have a heading relatively near what you are working on, then at any time you can click on that heading and jump to that location. It seems to me that it will be pretty rare that the outline itself changes so much that you can no longer see the heading for the section you are working on.
So keep that Outline visible, and have lots of fun headings in your docs, and you'll at least be a click away from your cursor.
Temporarly work on an outside document
This one is obviously just a compromise, but if there's lots of people editing the doc at once, it might be a good time to open up a text editor, work on your text there, then paste it in when you're done.
The downside of course is that if you do this, you are handing anyone working below you a stinker when you paste and their doc jumps down, but if the problem is that this you document is constantly jumping around right now, then just finding ways to type somewhere else for a bit can be part of the solution.
Alter your zoom level so you can see more
This one is obvious but I'll list it just cause there's no other answers here and it's relevant: You can always zoom out on the document temporarily so you can see more of it at once.
This will decrease the likelihood that your cursor goes completely outside your viewport, and help you use a little scrolling now and then to keep things in a workable position.