I love this idea! A higher-end Roku device may be a good option that competes with all the features and performance of the NVidia Shield ($199) or Apple TV 4K Wi-Fi + Ethernet ($149). I would buy it! Else I'll have to buy the Shield or Apple.
Roku technology is 100% problem, especially when trig to stream locally. 1 gigabit ethernet is required for large 4K movies.
As has been posted many times before: Roku's are designed for INTERNET streaming. You don' t need much more than 16-25Mbit. The Roku Media Player is about all you can use to play local media (not sure about Plex), but RMP is out of date and seems to be abandonware.
You can add Gigabit Ethernet to a Fire TV or even cheap Walmart Onn 4K Google TV. Plus, the Google TV can add alot of stuff from the Google Play store, and sideload even more. I have a Fire TV Stick, and a UGreen Ethernet/USB Hub on it. I also have an Onn 4K Pro Google TV. Although it has 100Mbit Ethernet built-in, I did the same adapter to it, mainly for the hub. On both, I get about 350-380MBit.
https://www.amazon.com/UGREEN-Ethernet-1000Mbps-Nintendo-Chromebook/dp/B00LLUEJFU/
That's the problem with Roku, instead of being so narrow minded for just "Internet" streaming, they need to think more broadly. Proof: why are the (outdated) Shield and the Apple TV 4k doing so well at their price points?
Where are you getting your Nvidia shield sales numbers? I searched around but I couldn’t find anything that pointing to high sales. I found it hard to find anything that even mentions them. For example, one market share chart showing Roku, Fire TV, Google Chromecast, Apple TV, and TiVo (in that order) left another 4% of “other”, which presumably Nvidia is part of. Not that I’m saying there’s anything wrong with the device, but it doesn’t seem to have sold in high numbers, which seems to be Roku’s focus.
In my opinion, Apple has long had a certain luxury/life-style/locked-in kind of status. I’m not sure that Roku could (or perhaps even wants to) break in to that market. For starter’s I think Roku’s customer support would need to improve a lot. 😀