Here are the steps:
1. Double-click BCM-EN (or whatever the name for current BCM installer file is)
2. Notice that it extracts data to C:\esomereallylongfoldername
3. Go to that folder, then into the sse folder
4. There will be a file called sqlexpr.exe or something similar
5. Run that file ignoring the main install wizard
6. Choose advanced mode when SQL Server Express setup opens and choose to create a named instance
7. Name that instance MSSMLBIZ - anything else will not bypass the SQL install process
8. Complete the SQL Server Express setup and check in services.msc (start -> run -> services.msc) that SQL Server (MSSMLBIZ) is started (check for other SQL-related entries with MSSMLBIZ if this one is absent)
9. Go back to the main BCM install wizard
10. Attempt to complete it. It should complete nearly instantly because this in our case made it bypass SQL server installation routines and BCM by itself is tiny.
11. Start Outlook and check if BCM got installed.
It was a pain to debug, but this was the only way we were able to reinstall BCM.
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