Unless you have unlimited budget I find that buying cheaper cards more often will give you better average performance.
You still have an idle graphics card, but you can enjoy the benefits of it from any laptop in your home network. My gaming desktop is wired, my Linux laptop is wifi, and I get 4K @ 60FPS flawlessly.
However, I would prefer not to have to upgrade in the future and offloading the intensive parts to Google would be highly preferable.
No matter how good Google's CDN network is, you can't compete with sub-1ms in-network round trips. There's not really any clever "latency compensation" you can do here.
Even if you rewind state to apply input, which games probably won't support anyway, that still only helps you close the gap added by internet latency. A gap that in-home doesn't even have in the first place.
This may result in a visual glitch, but you won't have missed your target.
Of course, the hardware you have to throw at it to do that quickly becomes ridiculous, unless you can come up with a way of efficiently rendering the multiple versions.
[1] https://www.libretro.com/index.php/retroarch-1-7-2%E2%80%8A-...
That said, I had my Bootcamped MBP with a XB1 controller connected over Bluetooth and any input lag was negligible with the Assassin's Creed Odyssey Project Stream demo.
What makes you think games would just be included in Stadia?
Competing streaming services here are around $10-20/month without any games included. Origin's game access is $15/month without any game playing hardware included.
So... what will stradia end up being, and at what price? Would you pay $30/month for this? When a PS4/Xbox is only $300-400 in the first place, and has a lifespan of ~5 years?
Origin isn't relevant to this conversation.
$15/month for a streaming service + $15/month for game access service equals, drum roll, $30/month.
What are you not getting here? Origin is relevant as a reference point for what the games themselves cost on a subscription.
Stadia still needs to actually pay for games, after all. Either as a subscription (reference origin's pricing), or you straight up buy them at the normal $60/pop.
So instead of spending $1500 on that piece of gaming equipment spend $250-300 instead. That's what you're actually getting here. A very slow CPU with a mid-range GPU. It's a budget build that's not going to drive 4k@60fps with the bells and whistles. Not remotely close. It'll be fine for 1080p gaming, though, but that's realistically it.
I want this to work.