Community Friendly Scorecard
I think it would be immensely helpful for XDA to provide a scorecard of how open to development and community-friendly various producers/lines of phones are.
Some phones you can expect are probably going to be well supported by ROM developers and other community developers for years, while others will likely never see much custom development.
Are the bootloaders on their phones easily unlockable? Is the kernel source code provided, complete, and current? Are they easy to root? Is their boot partition conducive to custom ROM installation? Do the companies supporting the phones have a good history of cooperation with community developers? Are community developers generally willing to take up support of devices from this company? Are the devices generally popular on XDA? All of these factors together can give a strong indicator as to what one can expect the community to look like in the future. Companies that are friendly (OnePlus?) would get an A. Companies with phones that are locked down (Apple) would get an F. Everyone else would be somewhere in between.
It wouldn't be feasible to maintain this for each and every phone, but I'm thinking it could be done for the main companies providing phones (OnePlus, Xiaomi, Huawei, etc.), or perhaps with differentiation between key lines on specific manufactures if there was found to be a significant difference between lines (Mi, Redmi, Poco, or Huawei P__, Mate, Honor, etc.).
I think this would be a really helpful resource to readers like myself looking to buy a phone and wanting some guidance as to what kind of community support they might anticipate throughout the life of the device. Furthermore, this would serve as a review/feedback to these corporations... rewarding those who are cooperative, and exposing those who are uncooperative, and perhaps incentivizing some better practices in the future.