Thought i should share my experience in this thread.
I migrated 300 clients this week with zero problems, the key that made my day was that i looked into the reconnect tool creation more closely.
the maketool.bat has a /silent parameter if you use that the reconnect.exe will not display popup after it is done and just quit, this made it possible to push this tool to every client that was connected to old management. Only issue is that the reconnect.exe exists with 1 and not 0 so if you push with anything that checks response add 1 as successful response.
they way i created the reconnect tool was that i created an export package in cloud management, downloaded the msi and unpacked it with 7-zip, searched the dir for config.dat it was named Binary.CPINSTADDEXT_config.dat.
Copied this file renamed it to config.dat and used it with maketool.bat with parameter /silent
One thing to note is that if the export package is configured to add computer to a virtual group it will do that also when you reconnect with the tool, i used this opportunity to cleanup some virtual groups when migrating.
Since nothing in this was sure to work did i check every client one by one, i was just happy to finally migrate and better it took a few more hours to be sure everything is ok.
Every client connected to cloud the second the reconnect tool was done, new policy was installed without issues.
Users did not notice any interuptions.
Important to state is that i did this on my own this was not initiated by Check Point in any way, i searched and read a few SK and decided to test and my backup plan was always to manually reinstall every client since that was the first migration plan either way.