From what I understand, this isn't possible, at least in how it currently works. Optimus-manager does many changes, it even modifies systemd somehow to make it all work. MHWD is rather a simple install and configuration utility so implementing optimus-manager would need a complete rewrite MHWD from the scratch and even rebuild it into more advanced and complicated tool.
From distro maintainer perspective, it's just not a good choice. Everything is in flux so additional tools must be simple to update them easily.
Additionally, optimus-manager needs MANUAL configuration so this beats the purpose of having it within MHWD where you rely on everything being set for you automatically.
Also, since there are countless hardware combinations, we can't be sure that optimus-manager will work smoothly with them all the time and this also creates different graphic configs that need to be manually disabled.
In theory, it all could be automated, but this would be susceptible to more problems than it is now. Manual intervention ensures you adapt it for your current hardware and setup situation.
With time, when hybrid drivers and linux kernel updates along with newer graphic cards that could do more advanced energy settings, hybrid setup will be a viable solution, because dGPU will be turned down or use so little energy it would be negligible. Till then, switching hacks that complicate things a bit are the best solution for old or current hardware.