You sound a like reseller to me...
So far I have instructed other members of this forum and the NFPS forums to change to portals that don't have Stalker Middleware 5, and in this case it is only Portal 1 for a limited time only.
You can't fight this upgrade it is happening whether you like it or not. I'm sure a new version of the STB Emulator is in the works but when it will be released is anyone guess. I have a feeling that the STB Emulator may be pushed out (unless mvas figures it out), and replaced by the official Infomir Emulator dubbed "StalkerTV" which is available for both Android and iOS device natively. The provider has to activate this feature and is a feature only available on Stalker Middleware 5.
Again these are my own personal thoughts, doesn't mean any of it will come true, it's just how I see it playing out.
Edit: Seems like changing MACs to 79 from 78 also does the trick for Portals 2-5. It appears like the 78 prefix coding has been overwritten with the upgrade and has to be reimplemented on the servers that contain Stalker Middleware 5.0.1. Which I'm not sure they are aware of as of yet, or they do know and have something else in store!