Possible plans of Boeing/FAA
[Not a pilot, but my brother was a FE on 707/727/747s so I am aware of some of the background and culture]
From the evidence and reading between the lines, it seems to me that the plan is to get just the FAA alone to certify the MAX only in the USA (and maybe neighbouring countries with some arm twisting?). The assumption will be that reluctance of certification from elsewhere is expected to collapse when it is proven that the MAX can fly safely. How effective this scheme will be is anyone's guess but I am sure flight crew will want to be 100% convinced of the ‘fix’ which from what we can glean is a simple software patch. If it involved hardware changes (new wiring) that would be a major certification issue surely?
What concerns me as a retired software dev/tester of over 30 years experience, is the blasé assumption that yet more code will fix this. We all have experience of another Seattle company that has a regular ‘Patch Tuesday’ that fixes what previous patches broke. I’ve never worked on safety-critical code but even run of the mill commercial applications take a lot of planning, test plans, and test cases and even then something comes out later to bite you on the bum. As for combining 2 FCCs, it’s not a trivial task.
I have worked for US companies such as Xerox and they used CMM (as it was back then, now CMMI) as a process to control software changes. This was for an embedded controller for a multifunction machine with greater than a million LOC. The thing is that this process actually worked! No change was so trivial that you did not have to run it past a meeting of peers and librarian and justify the change and potential side effects with a backout plan as well. So how did any code change on the MAX not get scrutiny?