Indeed it's possible to make a "fake ofw payload" based on HEN like I did with MAMBA.
It would be the same HEN payload except that it would start without CFW syscalls enabled and therefore without support for homebrews (prevented by the homebrew blocker). If the create syscalls hook is implemented in mappath.c (it is implemented in Cobra 8.3 & Mamba 8.4) then it would be possible to enable/disable CFW syscalls on demand without reboot.
Funnily enough, the first thing I wrote during HEN's initial development phase was a minimal kernel ROP payload that installs only lv2 peek and poke.
At the time the idea in my mind was to have a HEN composed of modular payloads rather than just a full HEN in one payload, the modularity would have enabled users to load whichever features they needed, there would have been a fan control payload, an iso support payload, a rif payload, etc..
Then Habib decided to port Cobra, a trivial thing for him to do given his hands on knowledge of Cobra, so I scrapped those plans and ended up giving up on HEN development altogether soon after that.
Having said that we could potentially revisit the idea.
The only obstacle to the modularity concept is that we would need to create a core plugin payload first, its role would be to orchestrate inter module communications by providing an interface to kernel modules, it is necessary for things like multi threading synchronisation and also for modules to be able to call each other's public functions or access each other's public variables.
Another way around this issue.might be to start making stub libraries for kernel payloads so that other payloads could link their exposed functions.
Neither HEN/Cobra or Mamba do address that problem either actually so the development of an inter kernel payload communication plugin would be a bonus to all existing kernel solutions.