I can't imagine how you'd implement an MMORPG as I'm not a tech savvy guy but I totally like this project of yours as imagining going from a computer specific game to a hand held console/mini computer like the Steam Deck is a huge breakthrough. I think it will open new opportunities and possibilities for us video gamers. I do, wish that a company like Visionary Realms considers this for a platform like Steam™️ Deck. This is pretty cool, man!
Moved to Off-topic mate.
Anything other than a PC/Laptop is probably not something we will include at launch unless there is an easy way for us to make it available but it will all depend on funding, Unity engine compatibility and resources. We would love to get Pantheon onto as many platforms as possible and support it but we have to be realistic and work within our means.
With some effort you can probably run it somewhat decently by installing windows and using something like Xpadder. Obviously the Steam Deck doesn't have a keyboard so having to use an on-screen keyboard for chat might not be the best user experience.
I did manage to make a usable setup for vanilla wow on a GDP Win for whatever its worth. The only advantage i can see for the Win is that it has a keyboard. Pantheon will almost certainly require more power to run than a game from 2005 but that APU in the Deck seems really capable tbh.
If VR released the game on Steam, Valve would likely help optimize it themselves. I just got a Steam Deck and games like Elden Ring work very well despite not working that well on Windows OS. That is a huge title that brings value to their hardware though, not sure if Pantheon will rate that high.
I think the most relevant part of this question is if VR plans to fully support controller's for play. Which they may not want to do. I'm not saying it won't be possible to use a controller, but the UI will be built around KB+Mouse and controller users will likely have some gimmick to use the mouse pointer as if they had a real mouse.
My take on controller support always is based on how it effects how the Keyboard+Mouse interacts with the UI. For example, in a game like Elden Ring, if you use controller you move through the UI by left, right, up and down to cycle through the menu options. Yet a KB+Mouse player can click directly on the option he wants without needing to cycle through. Yet some games force the Mouse user to still cycle through the options just like the controller player does and never has a mouse pointer to bypass this system to click directly on the option he wants. This means the KB+Mouse user is artificially limited because the UI is built for the limitations of the Controller.
This kind of intentional gimping the UI for Mouse users really irks me. True support for both allows the UI to adapt and work differently depending on the device you are using.
VR may not want to put in the resources to put in that full UI support for controllers.