Viewport Frames (in my opinion) have gotten very little attention by Roblox, they allow you to display basically multiple screens, and this has so much opportunities that are just not utilized by the current limitations. For example, a really cool usage of viewport frames would be to use it to highlight different regions. E.G highlighting a certain region in different lighting, (which, for a recent example of mine, could be used to convey your healing range) or it can be used to make certain elements of your screen ‘pop’ more. And something that I find really limiting is the lack of support for any sort of VFX on a viewport, which often mean that if I wanted to highlight something using viewport frames (where, Roblox highlights often fail because they don’t keep the original colour of the object), any VFX on the character usually doesn’t highlight. Furthermore, this type of compatibility will allow for developers to stop resorting into hacky methods to display VFX to the camera (like positioning it in-front of the camera).
Alongside adding VFX Support into viewport frames, It’d also be nice to have full lighting support for them (like depth of fields, blur effects, even perhaps a lighting mode). Considering Roblox’s alleged improvements to lighting technologies, this should be possible to do now.